_ The date shows when this yolume was taken.

ne

LIBRARY ANNEX nonce

for@nstruction or re-
search are returnable
within 4 weeks.

Volumes of periodi-
cals and of pamphlets
are held in the library
as much as pdssible.
For special] purposes
they, are given out for
a limited time.

Borrowers ‘should
not use their library
privileges for the bene- ~
fit of other persons,

Books. not needed
during recess periods
should be returned to
the library, or arrange-"

_ ments’ made: for their
return during borrow-
er’s absence, if wanted.

Books needed by
_more than gne person

are held on the reserve
list, :

Books of special
value ‘and gift books, °
when the giver wishes
it, are not allowed to
circulate.

HOME one RULES.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ey Laie saa

 

 

PAINTED INUS.A

 

 

 

 

 

GAYLORD

UL

wa

92
AMERICAN SOCIETY OF CIVIL ENGINEERS.

INSTITUTED 1852, :

 

TRANSACTIONS.

Norz.—This Society is not responsible, as a body, for the facts and opinions advanced in
. any of its publications.

 

547,

(Vol. XXVII.—September, 1892.)

RAINFALL, FLOW OF STREAMS, AND STORAGE.

 

By Dresmonp FrrzGrratp, M. Am. Soc. ©. E.
Reap June 81x, 1892.

 

WITH DISCUSSION.

The accompanying tables were prepared during the summer of 1891,
for the purpose of calculating the yield of drainage areas with varying
proportions of land and water surface. The results contained in this
paper are intended for use in Massachusetts. They may, perhaps, be
found applicable to a very much larger area.

Rainfall.—There is hardly any phenomenon about which so many mis-
statements are commonly made as that of rainfall. Hither, ‘the cutting
down of the forests is fast diminishing the annual precipitation” or
else the latter is ‘increasing rapidly from turning up of the ground,”
and other causes. ‘‘There are no longer such snow storms as we used to
have.” ‘‘The rains come now altogether in the spring.” ‘<* Freshets ’
and ‘droughts’ alike come from great changes in the rainfall.” These
and a multitude of other fallacies are constantly met with. As a
matter of fact, the annual rainfallis such a varying quantity that it is
254 FITZGERALD ON RAINFALL, ETC.

extremely difficult to lay down general laws in regard to certain of its
phases, even with the aid of a good rainfall table.

Again, the observations themselves are frequently inaccurate, as can
sometimes be told at a glance. The earlier results were generally too
small, because the gauges were placed too high and less care was exer-
cised to measure all the small showers and the snow. ‘Too often the
tables issued from official sources and stamped with the approval of
the Government are open to this criticism.* The periods also are gen-
erally too short to build safe theories upon; and, lastly, self-interest
connected with important commercial enterprises leads to false state-
ments. ,

Table No. 1 contains a compilation of seventy-four years of rainfall,
by months, in the vicinity of Boston, and is now first made public.
Another table, not here published, contains a record of rainfall observa-
tions 1852-91, made at Lake Cochituate, about 15 miles from Boston,
and Table No. 2 gives the rainfall on the Sudbury River water-shed
from 1875-90 inclusive.

Yearly Means.—The yearly means from these tables are as follows:

Boston, seventy-four years..........000ee00 47.00 inches.
Cochituate, forty years...... cee eee eee eee 47.98 <*
Sudbury, sixteen yearS..........cee eee eens 45.80 <«

An examination of the yearly fluctuations from these means, taken
in connection with the methods of making the observations, does
not disclose any definite law of increase or decrease. If there is a
secular change, it is probably too slight to be observed in a century,
especially where the observations are not all taken under exactly the
same conditions and those conditions such as experience has shown to
be necessary. The Providence and Lowell records make the average
for the year about 45 inches.

_ As there is a liability to underestimate rather than to overestimate
the rainfall,t the writer assumes that a general average for Boston
cannot be far from 48 inches, or 4 inches per month.

Maximum and Minimum Rainfall. The largest annual rainfall re-
corded in Table No. 1 occurred in 1863, 67.72 inches, and the smallest
in 1822, 27.20 inches. If these figures are correct, they show how great

 

*The Signal Service observations of rainfall made on the tops of high buildings are
untrustworthy,

{Largely from placing the gauge too high above the surface of the ground.
FITZGERALD ON RAINFALL, ETC. 255

the range is. They cannot be far from the truth, because in 1883 the
record of 32.78 inches on the Sudbury is corroborated by the record of
many gauges, and the rainfall tables of Lowell, Providence, Waltham
and other places all point to a minimum of about 30 inches. The
writer has ascertained by an examination of the original records that
the rainfall recorded at Waltham, of 26.9 inches, in 1846, included ten
months only, and that the record at Lowell of 28.46 inches in 1825
contained nine months only. Such facts as these are sufficient to
make us exceedingly cautious in regard to records. In a general way
it is safe to say that the yearly rainfall varies from 30 to 60 inches.
The minimum monthly rainfall was 0.23 inches in September, 1884, and
the maximum properly recorded in any one month is probably not far
from 12 inches.
Monthly Means.—The following table shows the monthly means:

 

  
  

 

Boston, 1818-91. Oe | SupBuRy, 1875-90.

DADUALY iiesoas vat eneae eNews 3.98 3.88 4.18
Febru ary iisemies careesiew selena’ 3.78 3.62 4,06
DMB es vacccersisiciS pase seesciers side wieiste 4.36 4.25 4.58
DUM eras ie seiestie Sra oi Fiareia ata wah cestasecs 4.06 3.97 3.32
May 3.79 3.87 3.20
TATIG cost: winiy wate B 8ieres diarn Wore oie 3.27 3.31 2.99
July... 3.71 4.23 3.78
August 4.39 4.94 4,23
September 3.55 3.59 3.23
October... 3.84 4,29 4.41
November .. 4.31 4.44 4,11
December 3.96 3.59 3.71

47.00 47.98 45.80

 

 

 

 

 

The progress of the monthly fluctuations can be seen in the diagram
on the following page (Fig. 1).

There is a strong similarity in the profiles, too decided to be the
subject of chance. The Providence rainfall (1832-91) has been added
in a series of small circles.* They correspond to the general form of
the other lines.

Whatever doubt we may have in regard to individual observations,
the general accuracy of the average monthly distribution must be con-
ceded. Longer observations may change the maximum and minimum
points, but the present weight of evidence seems to favor March,
August and November for maxima, and June and September for minima.

 

* The Providence rain gauge previous to 1876 was 7 feet above the ground, and must
have given too small a result,
ETC.

256

‘L -DET

 

bo 2ehS ‘ony Amr annr AW

 

 

 

 

 

 

 

 

 

 

FITZGERALD ON RAINFALL,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

*s100A G9 B2LePI.
ae os
x x
g 3
= =
i 49
= ea
S
: 3
ae
Ae
2 é -
220 lags ‘opy Ant INA Ay “voy
‘ALINIDIA ONY NOLSOG 4O TIVINIVY ATHLNOW NYZ/AI

 
NSS
yar

 

=

x a Lh ¥ rk fi

Gan ae an
EP | ic Nk

ACT TEI oa NBN ESS
t

 

2 : f
3 aN biesZ
h I LP
(
Ca \
Wy Vy \

A j
CITA
ay {| G} akAY

\ VE

 
 

         
   
     

  

SBYRG

=
aE
a
S %

S)

eZ
a
Ly
Au
Aa
7
LZ

)
7
\s

DY MAP OF THE
x SS SUDBURY AND COCHITUATE
x 3 WATER SHEDS

si REDUCED FROM THE

yw) STATE MAP.

yr 1890.

  

LF
Ae
SY

GW

 
FITZGERALD ON RAINFALL, ETC. 257

Seasonal Distribution.—The seasonal distribution is as follows:

 

 

 

  

Boston, CocHITUATE. Supboury.
SPU Bis teria jsc@oseeataonwae 12,21 12.09 11.10
Summer.. aaies 11.37 12.49 11.00
AUMUND wis ccintar taiteccmacieeuis 11.70 12.31 1175
Winter... 11,72 11.09 11.95

 

i

 

 

From these figures it is obvious that the rainfall is evenly dis-
tributed through the seasons of the year.

Evaporation.—The total flow of a stream must equal the rainfall,
less the evaporation and other losses. As the latter are generally insig-
nificant, the difference between the rainfall and the rainfall collected,
is the total evaporation from the water-shed supplying the stream.
The average of a number of years shows us that from 45 to 50 per cent.
of the rainfall flows away in the stream; and if the average rainfall is
48 inches, then about 24 inches are evaporated yearly from the ground
and other surfaces ordinarily found on a water-shed. The evapora-
tion from a water surface is greater than that from the ground. Table
No. 5 is an attempt to represent the monthly evaporation from a water
surface during the period embraced in the other tables. The data
upon which the table is founded are taken from a paper on ‘‘ Evapora-
tion,” published in the Transactions of this Society in 1886 (Vol. XV,
p. 581), but some observations made since the paper was published
have been added. Itappears from the table that the mean evaporation
from a water surface in Boston is 39.2 inches, or about 82 per cent. of
the mean rainfall, although it must be remembered that there is no
connection between rainfall and evaporation. The diagram on page
258 (Fig. 2) is a new diagram of mean evaporation, which contains
additional data on that already published.

Description of Water-Sheds.—The topographical map (Plate XLV)
accompanying this paper gives an idea of the nature of the Sudbury
and Cochituate water-sheds, but a few words of description seem
necessary.

The Sudbury River water-shed has an area of 75.199 square miles;
the Mystic, 26.9 square miles; and the Cochituate, 18.87 square miles.
They together form the sources of Boston’s water supply. The
Sudbury is hilly, with steep slopes. There are, however, some
large swamps within its borders. The Cochituate, although adjoining
258 FITZGERALD ON RAINFALL, ETC.

the Sudbury, is entirely dissimilar. The slopes are flat and sandy.
Its surface is mostly modified drift, while the Sudbury is largely com-
posed of unmodified drift. The Mystic water-shed lies to the north of
Boston, and about 30 miles distant from the other two sources which
are to the west of the city. Its surface is steeper than the Cochituate,
and not as steep as the Sudbury.

MEAN MONTHLY, EVAPORATION CURVE,

 

Fie. 2.

Flow of Streams.—However uniformly the rainfall is distributed, on
the average, throughout the year, the effect of the excessive evapora-
tion during the summer and of the frozen ground with accumulations
of snow from month to month in the winter, is to produce a most
irregular flow in the streams. During seven months of the year, from
November to May inclusive, the streams have a large flow, and during
five months, from June to October, a small flow ; but it is in February,
March and April that we must look for the very large yields.

Table No. 15 contains the yields of thethree water-sheds for various
periods and combined in several ways. The results are different in
some particulars, but in general agree sufficiently wellto form the basis
for an instructive investigation. The widest variation that is found in
the tables, exists between the Sudbury and Cochituate collections. On
the average, the latter collects 12 per cent. less water than the Sudbury.
It is probably true that the Sudbury water-shed gives a somewhat
larger yield than the average water-shed. It collects much more in
the spring than the other two water-sheds, and rather less in the
summer. It is impossible in the limits of this paper to go into an
FITZGERALD ON RAINFALL, ETC. 259

extended discussion of the causes leading to these differences in collec-
tion, but the writer has thought that a better average, or typical col-
lection, would be obtained by uniting the results of all three.

Monthly Yield.—In the diagram on page 260 (Fig. 3) the average
monthly yields of the three water-sheds have been plotted for the
period 1878-90, inclusive. The heavy line is a mean of the three, and
for convenience the values are here repeated with their equivalents in
cubic feet per second.

YrewD or a Typican New Eneuanp WaTeER-SHED PER Square Mine,

 

 

 

   

 

GALLONS, Cubic FEET PER SECOND.

TANUATY . 20. cc eee ee ee eee eee es 37 387 000 1.866
PODPUALY scsesceca-aveions veces epsiararainioss 55 056 000 3.042
March ieee Pe Sites 71 226 000 3.555
April 49 107 000 2.533
May 30 406 000 1.518
June 14 975 000 0.772
July xis 3G wile 7 491 000 0.374
AUG USE ces ges srenins aes oe cnorT 11 399 000 0.569
September 3 10 242 000 0.528
October... 16 797 000 0.838
November a 24 787 000 1,278
December. ...... cccsesccccenes 34 128 000 1.703

Total and Mean........... 363 001 000 1.539

 

 

 

 

It will be convenient for many purposes, especially where ques-
tions connected with the use of water for purposes of power are
concerned, to use these monthly results in the order of their magnitude
as follows:

AvERAGE Monruty YIELD PER SquaRE Miz In ORDER OF MAGNITUDE,
Cubic Feet per Second,

 

Jal y's: cawen see ses ad ware 6 on bee 4 dee t's tale ea Sie 0.374
September .......cce cee ceeeee rece ereeeceeerenee 0.528
AMPUBE ss oae ee aiiee badoe ¢4sien Uordiee y- Yee eee es 0.569
JUNGAs . sea d csatewtecse DAVES Se <hewsestinwes eee ss 0.772
OCU DER oie diheseieraeaits Ga awniGuse abies werd 5.eaunend Sa aerate 0.838
November... ses sce s weae s tae cs Sees See ee eiesie 1.278
May wcnewiigucdcntuwde eae ates Stnas sete ta dewe F 1.518
December. ......ccceceeee cece cecenreneteereenes 1.703
AES: iy 1.866
April cies scissors sae ce eee es Salted « Sisleis nla Cane ae cee Ba 2.5383
February... .. cee cece cece cece cence tenet e tenes 3.042
Marelis:.ccccavacies veew te meds ease eee ee eee ee Hows 3.555

MG@an..ccei eva cya cee oo abde te tis ee Poe 1.539

Fig. 4 contains the above quantities in graphical form.
 

 

 

 

ETC.

 

Of

 

 

 

OS

 

 

OF

 

‘IUW FAMNOG HF SNOTIVD JO SNOITTIW

FITZGERALD ON RAINFALL,

0S

09

 

 

260

[ora

 

OZ

 

 

 

 

 

 

 

 

 

 

 

 

Oc

 

 

 

q)

‘SQ3HG YILVM JIL

wo

AW ONV BLVALIHDOD SAYNEAGNG 3HL 40 SANZIA A

VO/T7Y

“FVUW FYWQOG WFd SNOTTRDD .
Fia. 3.

 
FITZGERALD ON RAINFALL, ETC 261

The average yield of the Sudbury River water-shed alone for sixteen
years is 1.669 cubic feet per second, which corresponds very closely
to the Croton water-shed mean of 1.626.

The month of May represents the mean monthly flow for the entire
year.

Ordinary Flow of a Stream.—The ordinary flow of a stream certainly
does not mean the average flow, for one or two heavy freshets occurring
in a few days in the spring of the year have a great influence on the

&IMySTIC WATER -

 

Fie. 4.

average without affecting in any way the ordinary run of water.
The large flows above the average, occurring at the summit of the
diagram (Fig. 4), in the months of February, March and April,
should evidently be excluded. The flow in July is too insignificant
to be considered. If we take the months above the average, at the
average rate, and add to these the months below the average, excluding
the month at the bottom ‘of the list, and divide by the whole year,
we shall, in the opinion of the writer, get a fair ordinary flow of the
stream.
262 FITZGERALD ON RAINFALL, ETC.

Applying this rule to the results already obtained we have:

Gallons,
September......... 10 242 000
AUBUSb scgies anaes se 11 3899 000
JUNE 6 6 SaHe es ces 14 975 000
October ........... 16 797 000
November......... 24 787 000
MEA ccesesiss o o:avere «... 380 406 000

Five months of mean flow, 149 178 000

257 784 000 — 365 = 706 000 gallons per day,
or about 1.1 cubic feet per second per square mile.

Maximum Yield.—On the average, March is the month of maximum
yield and its flow is about two and one-third times the mean monthly
flow and about one-fifth the entire flow for the year. In March, 1877,
the Sudbury water-shed (Table No. 8) yielded 149 222 000 gallons per
square mile, or 7.448 cubic feet per second per square mile; about
one hundred times the minimum monthly yield. This flow averaged
4 807 000 gallons daily per square mile for thirty-one days. It is the
largest flow recorded for a month in the sixteen years.

Frreshets—The greatest freshet occurring on the Sudbury water-shed
took place February 10th-13th, 1886, and a full description of its effects
can be found in the Jransactions of the Society for September, 1891.
The maximum yield for twenty-four hours was equal to 1.54 inches in
depth upon the surface, or 26 763 260 gallons per square mile, or 41.4
cubic feet per second per square mile; and the maximum rate of yield
was equal to 1.646 in depth on the water-shed in twenty-four hours, or
44.2 cubic feet per second per square mile. On March 26th, 1876, a
freshet giving nearly the same yield occurred, go that it is not probable
that this amount of rainfall collected in twenty-four hours is very
unusual,

Gaugings on a small affluent of the Sudbury, embracing 6.434
square miles of surface, showed a similar flow per square mile to that
in the main stream. The maximum rate for twenty-four hours in the
small affluent was equal to 1.801 inches of depth on its drainage area.
Although these freshets were considered very disastrous in Massachu-
setts, they cannot be considered large when compared with what has
been observed in neighboring water-sheds. Freshets of 3 and 4 inches
FITZGERALD ON RAINFALL, ETC. 263

collected in twenty-four hours are within the experience of many
hydraulic engineers, and it certainly would not be safe in designing
dams to provide for less than 6 inches collected in twenty-four hours
and flowing continuously, or 104 272 440 gallons per square mile per
twenty-four hours, or 161.3 cubic feet per second. These remarks are
of course applicable only to an ordinary New England water-shed not
covered with houses and streets. The water-works engineer who is
constantly designing waste weirs, dams, reservoirs, etc., may find it
convenient to bear in mind that one square mile of land surface yields
approximately 1.5 cubic feet per second throughout the year and that
the maximum freshet flow may be one hundred times this amount or 150
cubic feet per second. In millions of gallons these become one million
and one hundred millions respectively.

Minimum Yield.—The minimum daily yield of a stream is a dangerous
subject for figures. There are so many conditions tending to affect the
daily flow, even on the average water-shed, that it may often be some-
thing that man controls by his use of mill dams, storage basins, etc.
Taking a period of a month, the Sudbury has shown in September, 1884
(Table No. 8), a yield as small as 1 318 000 gallons per square mile,
or 43 930 gallons daily per square mile, equivalent to 0.068 cubic feet
per second per square mile. The water surface during this month was
0.0303 of the total area.

Clemens Herschel, M. Am. Soe. C. E., reported to this Society in
July, 1881,* that the Connecticut River, with 3287 square miles of
drainage area, had discharged as low as 0.306 of a cubic foot per second
per square mile. Other large rivers in the country have shown a lower
yield than this.

The discharge of a small water-shed, say, 2 or 3 square miles in area,
in a protracted drought may be practically nothing. The geological
formations on a water-shed have an important bearing on the minimum
yield. If there are large plains of loose gravel or sand which hold
water, and whose water tables are drawn down in the summer, the
minimum flow is larger than where the same areas are occupied by
unmodified drift.

Average Daily Yield.—It is apparent from an inspection of the tables
that the average daily yield per square mile of an average water-shed is
about 1 000 000 gallons, or 1.5472 cubic feet per second.

* Vol. X, Transactions, page 238.

 
264 FITZGERALD ON RAINFALL, ETC.

Percentages of Rainfall Collected.—Percentages are almost as danger-
ous to deal with as the minimum flow. In many ways percentages are
instructive. They bring home forcibly to the mind the relation existing
between the rainfall and the flow in the streams at different seasons of
the year, but their results must be interpreted with a knowledge of the
prevailing conditions.

Table No. 4 contains the monthly percentages of rainfall collected
on the Sudbury for sixteen years. To the general monthly averages
of this table, the monthly averages in the Cochituate water-shed from
1863-91, inclusive, have been added in the following table for purposes
of comparison.

Mean PERCENTAGES OF RAINFALL COLLECTED.

 

 

 

  
 
 
 

 

Sudbury, 1875-90. Cochituate, 1863-91,
Per Cent. Per Cent,

DADWALY: 212.23 sere varaseureya thn Syeivacdehisians Seseieyna od 49.1 53.1
February . K 78.2 71.9
March.... 109.6 84.6
April..... ‘a 109.1 83.8
MAY. sic maces tease forsargisrais engr “we Plates ieiatersin gia stewie 62.3 47.9
June igi 29.1 27.9
IWS caesar F 8.9 13.1
August... 13.0 17.7
September... 14.2 23.5
O CUODET a cinzirert acaisig iets dinrd dlenveinieirned aie 23.1 23.6
INO VGH OR esa rea ecelessssensere-svererauiere-aceeseian aula are ves 39.5 34.0)
DeCOmb eh ics cresersie'eswiccinre minleivin oie einsese mee Wit Kinlatnce 62.5 49.9

Mean sisacinsaniresauseeswsinescivicae 49.5 43.8

 

 

 

 

The percentages exceeding 100 are caused by accumulations of rain-
fall, generally in the form of snow, from one month to another, passing
off finally in a different month from that in which it fell. In consider-
ing monthly collections, it must not be forgotten that the amount of
rain falling in the previous month has a large influence on the col-
lections of the month following, especially in porous water-sheds. A
knowledge of this fact will often explain what seem to be anomalous
results.

The yearly percentages of rainfall collected on the Sudbury have
varied from 31.9 per cent. in 1880 to 62.2 in 1888, and on the Cochituate
from 25.7 per cent. in 1866 to 69.1 per cent. in 1891. The mean for six-
teen years on the Sudbury is 49.5 per cent., and for twenty-nine years
on the Cochituate 43.8 per cent. The percentages depend upon the
PLATE XLVI.
TRANS.AMSOC.CIV.ENGRS.
VOL.XXVII.NO 546.
FITZGERALD ON RAINFALL.
FLOW OF STREAMS & STORAGE.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

—T T
28 +- / 4 | + + + + +——4.
27 ail +— | T +——t +———
26 — T + =
25 T oooh
24 T
23 j
2at | { | t
2 / I “I
2o —t 1
‘9 T T +
j
' 4 + +
ra iy e
i fr / é | ial
dis 5 - : , } + et
tis g # y 8 y of Pah
$ a 3 & jf g y
es + fay ¥ © I | | |
o
ba 3 + pea
8 2 + 7 — ay
c | iL Be _L L
te S20. 540 S60 S8 660 620 640 660
410, jel | fr)
9 T T 3
* | . STORAGE CAPACTTY
7 e [ i required to Sustain Drafts
. ¥ of 100000-800000 Gallons Daily from
; ir One Square Mile of Water Shed
“ — * Containing Various Percentages of Water Surface
. | | + +—+ 3 Based on greatest droughts occuring on the Sudbury River
Water Shed 1875-1890.
2 1 + 2
May 1892.
: T a a | | i ; Desmonp FitzGera_o.
0 20. 40 60 700 ~~ 2o~C4O~CGO ~~ 1BO.~C oo ~C~COSCRO cai Soo Sto 340 S60 S60. 400. 420.440 460480 Sco ——

MiLtiona of GéLLons Sromoe
FITZGERALD ON RAINFALL, ETC, 265

distribution of the rainfall throughout the year. A heavy summer
rainfall and a light winter rainfall mean a small percentage of collec-
tion, and, conversely, a light summer and a heavy winter rainfall mean
a large percentage of collection, so that the total rainfall for the year
is but a partial index to the yield of a water-shed.

If, on the average, 11 per cent. only of the rainfall in July is collected,
it becomes evident that the amount of the rainfall in that month, speak-
ing within ordinary limits, is of but little consequence for most pur-
poses connected with water supply; and, still further, it may be said
that for systems which depend upon storage, it is not the summer
droughts which are to be dreaded, but the winter and spring droughts;
for it is the flow in these months upon which we depend to fill the
reservoirs. In July, 1876, the percentage of rainfall on the Sudbury
fell to 3.6.

Storage.—Owing to the great variations in flow, as already shown,
the question of storage becomes of great importance in schemes which
look to developments of available supplies from water-sheds. In a
report made by the writer in 1887 on ‘‘ The Available Capacity of the
Sudbury River and Lake Cochituate Water-Shed in Time of Drought,”
a method of showing graphically the storage required in the periods
of deficiency from 1875 to 1887 was given, in the form of a mass curve
after Rippl.*

This curve is found by plotting the differences between the yields
and the daily drafts. By this method the storage required for the given
daily draft in the periods of deficiency is easily found.

By means of Tables Nos. 11 and 13 (pages 281 and 283), which give
the yield of the Sudbury water-shed for sixteen years, by months,
reduced to 1 square mile of land surface and 1 square mile of water
surface, it will be possible to find the yield of any water-shed,
whatever its ratios of land and water surface.

Having found the yield, it will then be an easy matter to ascertain
the extent of the periods of deficiency for any given draft, or the periods
when the yield is less than the draft. To save the trouble of these com-
putations, the table (page 267) has been prepared, showing at once the
maximum storage required to tide over the droughts between 1875-90,
and for different daily drafts from 100 000 to 900 000 gallons, and ap-

 

* W. Rippl. ‘‘The Capacity of Storage Reservoirs for Water Supply.” Min. Proc. Inst.
C, E., Vol. 71, p. 270.
266 FITZGERALD ON RAINFALL, ETC.

plicable to different percentages of water surfaces found upon the given
water-shed. The table is reduced to the unit of one square mile, so
that a simple multiplication will give the required storage upon any
given number of square miles.

As the greatest period of deficiency or the most prolonged and
severest drought is the one on which this table is based, and must
ever be the one to which the cautious engineer turns for instruction, it
may be interesting to remember that this period from 1875 to 1890, in-
elusive, contains two years of most remarkable drought, following
each other closely. These were the years 1880 and 1883; in fact, the
period of yield from 1879 to 1884 forms a crucial test or measure of
what may be expected in the future. The value of exact measure-
ments during this period will be the better appreciated when we take
into consideration that the rainfall records for sixty years, 1830-90,
give no evidence of any more severe period of drought.

Of the future certainly we know nothing ; but, judging by the past,
we may feel assured that we have done all that a reasonable care de-
mands, if our works are proportioned to the maximum drought occur-
ring in so long a period as sixty years.

The following is an example of the use of the table. Suppose we
have a water-shed of 40 square miles which contains 10 per cent. of
water surface, and we wish to draw daily 500000 gallons. The
question is how much storage must be provided. Look in the left hand
column for 500000, and follow this line to the column headed 10 per cent. ;
here, we find the figures 90 550 000 gallons storage per square mile, which,
multiplied by 40, gives 3 622 000 000 gallons—the required storage.

The diagram Plate XLVI, which is a plot of the table under discus-
sion, will facilitate the taking out of quantities for intermediate per-
centages not given in the table. The horizontal lines are the ratios of
water surface. The perpendiculars dropped from the intersections of
these horizontal lines with the various lines of draft will give, at the
bottom of the diagram, the required storage in millions of gallons.

When storage reservoirs are distributed on different portions of a
water-shed, it is important to consider them with reference to their
positions, the extent of their individual drainage areas, and their
capacities for yield in connection with the other portions of the water-
shed; and these studies afford some of the most interesting problems
for the water-works expert. It is believed that the data collected in
this paper will give the means for solving these problems.
267

FITZGERALD ON RAINFALL, ETC.

 

 

 

000 FFZ LLO | 000 9FL 909 | 000 SFG 9E9 | OND LOS SOF | 000 ZS6 LEF | 000 SFE TIF | 000 066 S8e | 000 S20 09E | 000 SLO FES 000 006
000 F#6 T62 | 000 OFF TZG | 000 EFG OSF | 000 LSE O8E | 000 ZOZ FZE | 000 SGI 8ZE | 000 OFZ ZOE | 000 SLB 9LZ_ | 000 8zE 096 000 0¢8
000 #F9 909 | 000 OFT 9E% | OOV EEO SUE | 000 O9F LEZ | 000 ZF OLZ | 000 GFF FFZ | 000 F00 GIZ | QOV LZF 80% | 000 9OT 66T 000 0u8
000 FFE 12h | 000 9#8 OSE | ONO EFE O8Z | N00 LBL 1ZBZ | 000 LNG TIS | 000 1€9 00% | 000 FS0 OGT | 000 LLF GLI | 000 006 89E 000 OSL
000 #70 96 | 000 OFF G9% | 000 FLZ GIZ | 000 LES ZET | 000 LEZ ZBE | 000 189 TLT | 000 FOL 19T | OVO L2G OGL | 000 096 6ST 000 00L
000 FFL 08% | 000 OLL 9I@ | 000 FZE OGT | 000 188 S9T | 000 LOE SLT | 000 TEL SFI | 000 FO ZEL | 000 LL9 IZLE | OOU 19% FIT 000 o¢9
000 89% FIZ | 000 0%8 LET | 000 FLE INT | 000 LEG FET | 000 LEE FEI | 000 T8L SIT | 000 SOL 9OL | 000 249 SOT | 000 199 OOL 000 009
000 @I§ S8L | 000 OL8 SGT | 000 F&F ZET | 000 486 SOT | 00 8c6 86 000 T&G 66 900 $06 26 000 LL8 68 000 890 88 000 o¢¢
000 Z9E 9SL | OVO 0Z6 GZT | 000 FLF FOL | OVO OSE 06 000 EFT 98 000 Isl 28 000 SOL 6L 000 88% LL 000 €08 9L 000 00g
000 Z@IF LEE | 000 0L6 OOL |; ONO Z1E 68 000 008 8b 000 €68 SL 000 88% 69 000 9%9 99 000 880 99 000 €99 $9 000 O96
000 680 66 000 920 88 000 Z90 LL 000 0S0 99 000 SF9 19 000 99F 89 000 309 S¢ 000 884 29 000 €08 Tg 000 00F
000 L96 18 000 %¢8 SL 000 G18 ¥9 000 LEL Fg 000 0€9 09 000 99L LF 000 206 FF 000 LEO 2% 000 €LT 68 000 Og
090 L08 &L 000 20L 99 000 669 #9 000 Ler SF 000 06 6& 000 990 LE 000 20% F€ ono LEg TE 000 ELF 8% 000 008
000 998 TL 000 Fo 8g 000 6FF °F 000 8Eg EF 000 08% 63 000 998 9% 000 209 &@ 000 LE9 0& 000 166 LT 000 092
000 994 $9 000 Far 29 000 €80 6¢ 000 GFL S3 000 LF 02 000 999 SL 000 208 ZT 000 LE6 6 000 L6L 8 000 00%
000 999 69 000 #38 9F 000 §86 @& 000 ZF9 61 000 269 ST 000 €L4¢ IT 000 ZS9 L 000 ITIL 000 900 € 000 OST
000 G99 eg 000 #63 OF 000 €88 93 000 B10 ST 000 66 OL 000 €L6 9 000 989 @ 000 68% T 000 FI 000 GOT
*yaeo zed gz | *3ua0 10d 9% | "300 19d eT | “3u990 10d oT *yua0 10d g “yuo aad 9 *yu00 Jed F -4m90 10d G *yue0 god g | ‘yyviq [ted yuBsa0D

 

 

 

 

 

 

 

 

 

 

 

‘SMOTIVH “G "Q—'sIva_ woee4yxIgG—“peyg-19jyeM, soaTyY AInNqGpug uo peseg

‘HOVEUNG YALVAA JO SHOVINDOUTG SAOIMVA ONINIVINOG

GUY, Fvadg ANOQ WOW Livuqd ATV] INVISNOQ V Nivisog OL aguMIndaY ALIOVaVO TOVUOLG DPNIMOHG FIAVY,
268 FITZGERALD ON RAINFALL, ETC.

In a valuable report by Mr. Frederic P. Stearns, M. Am. Soe. C. E.,
to the Massachusetts State Board of Health, on ‘‘The Selection of
Sources of Water Supply,” the author has given a series of diagrams
illustrating the fluctuations of a reservoir caused by different daily
drafts. These diagrams show that, no matter what the extent of the
storage may be, the effect of drafts beyond, say, 600 000 gallons daily
per square mile, is to keep a storage reservoir below high water for
several years.

The importance of this warning cannot be too strongly impressed
upon the engineer who is designing systems of storage. The following
table, calculated for 0, 10 and 25 per cent. water surfaces, shows the
length of time that a reservoir would be below high water during the
sixteen years we are considering, and under various drafts.

Prriops Durinc WuicH any RESERVOIR WILL BE BrLow HieH WATER.

 

 

 

 

PERCENTAGE OF WaTER ON WATER-SHED,
Daily draft per
square mile, 0
per cent.

Covered Reservoir, 10 per cent. 25 per cent.
100 000 gals 14g months, 64, months. 714 months,
150000 “ ... 3% we Th ae 845 o
200 000 ‘* 73 “4 Tg ss 834 as
250000 « .. Ths ee 8% se 836 ee
300000 ‘* .. 84 - 846 ue 84 8
350000 “* 9% i 934 re 94 “
400 000 «* 9% « 0% « 10% “
450 UU“ 93g ES 1032 s 1 year, 914 as
500000 9}, a 10% es Le Oe iG
550000 “« 9% es lyear, 944 ae 1 “« 1013 “
600 000 ** 1034 ss 1 9M a 1 « 1036 ce
650 000 « 1034 “ lL © 9% “ 7 « 8z “
700000 « lyear, 94% 1 “10m « 8 * 101% «
750 000 “ well dE ION ee TTL 34 « 9 The “
800 000 “ [4 10% a m Bie ee 10 * 61% “
850 000 «« 6 ™ By 2 841 # Wo gy oe
900 000 7 © 9% re 9 BY ae Probably about 13 yrs., 9mos,

 

 

 

 

 

 

As it is undesirable to keep the water below high water for more
than two years in succession, it will be seen that, no matter what the
extent of the storage may be, it is impracticable to secure more than
about 750 000 gallons daily from 1 square mile of water-shed containing
10 per cent. of water surface. As there are circumstances which
permit of a different method of managing a storage basin and,
where the bad influences of keeping the water low for several years
are immaterial, the table for storage is carried to 900 000 gallons daily
draft. With this draft a basin on the Sudbury River water-shed
would have been one hundred and six and a half months or nearly nine
FITZGERALD ON RAINFALL, ETC. 269

years, without filling to its high water-line during the period 1875-90,
and a heavy growth of vegetation would undoubtedly have sprung
up on the exposed margins during this long interval.

To secure this draft a storage of 377 800 000 gallons per square mile
becomes necessary, which, if provided, would change the percentage of
water surface from 3} to 12 per cent., reckoning depths usually found, and
requiring an increase of another hundred millions of gallons tothe storage,
which in turn requires another correction for increase of water surface.

The writer has had an opportunity to apply the calculated yields
from various percentages of land and water surface to three water-
sheds—one with no water surface, another with 5 per cent. of water sur-
face, and the third with 25 per cent. of water surface. Daily gaugings
of flow were made for sixteen months, with the results shown in the
following table:

THREE WATER-SHEDS WITH VARYING PERCENTAGES OF WATER SURFACE.
Ratios of Calculated Yields to Weir Measurements.

 

 

 

  
 
 
 
 

 

 

0 Per Cent. | 5 Per Cent. |25 Per Cent,
1890; —PEBIUARY 556.56. odie sawsiee vinnie sa aieaeicie’s peea ba 0,957 0.934 0.958
March 0.925 1.031 1.005
1,056 0.965 0,864
0.945 0.865 0,859
1,297 1.029 0.634
13.391 0.713 1.742
August,..... 4 320 0.548 —0.277
September . 1.041 0.885 1,045
October... 0 850 1.110 1,164
November 1,201 1,343 0.982
December... < sate 0.950 0,909 0.908
USOL STA NUALY i c.ereisie sn esersivisiere saree wre Paine mwa ne Mawardaceers 1.034 0.983 1010
February. oc 1,070 1.009 0.996
March 1,012 1.141 1.028
April 1,060 1.095 1,018
May 1.024 0.821 0.578
1.014 1,023 0.977

 

 

 

 

 

With the exception of the 0 per cent., these ratios are thought to be
satisfactory as showing the general accuracy of the data on which the
yields for different percentages of water surface are based. A large
swamp upon the water-shed, with no water surface, probably caused
the failure in the case of the 0 per cent., which, however, is somewhat
magnified in the table by the fact that the yield was small, though the
ratios are large. The writer is inclined to caution engineers against the
use of the table for 0 per cent. of water surface on account of the difficulty
of finding areas of any great extent free from ponds, swamps or marshes.
It is doubtful if it is advisable to use anything under 2 per cent.
ETC.

FITZGERALD ON RAINFALL,

270

TABLE No. 1.

Boston Rarwratu—74 YEaRs.

Carefully collated from original records.

Snow melted and measured.

1818-23. Dr. Enoch Hale.
1823-66.

From 1823 to 1856 taken from Am.

Jonathan P. Hall.

Vol. VI, n. s., pp. 229, 308.*

Acad. Arts and Sciences Memoirs

1866-85. Supt. of Sewers.+

Boston Water-Works.

1885-1891.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BOR ee ees era te, Te Wine Te NGyee, ONE Ps eP AEs, LERNER GAL eat She Sie a Oa CaP ce Se ue. ee Te. et Ae fee ua, ie, elie we
AWAHAOSr OW HDAONNOEAEONMATAGEARAPOrOROCOMAHEDNOANOGOADNHONEAESHHAOBOOH
OTF LOT | Hod HD CAH OD CO HH GO ma HD HOD OD CD HCD SH SH SHH GD OD HN HSH HO HH HHH 19 19 10.19 11H OOOO HH IND OG HIS 1
DMOMOMODOMOOOMMODONOOMMOE-OANDANMNHOHOW AN ANDOMEONMMADDOOAWA on
CANA AMOANAA MOM ONIDA HID AA HAS O HD 100 09 09 10 HOD 10 HON 09 0 HD HIND HO LOND OW HH AAI 09 0D 19 1
ANONDANATHOANOCEDODDMMMHAMNKGHOHNOEANMOAREVMSOrANDOrONDSOANIAHOOHAH
FMOMPAMNMNHHODRNDADONEHDADDSOONADOHNOSCSOHMAADNHSCSOVWMOOHMONNOMHONDOD
Te MM ac Rac Srl acer aac wa aca Ik pl Da ec es a
AMOAAGDAMDMOAAAAAOHAAHAHAHOAHNMOWMOHHAODAAWADAAAAMIOANAHMOHONONOO OHIO
ARAMMOMOMOMHANNI ME DH HHOEFONAHDMDMMOHNOHNHSOHWSOMSONSCHENAASCASCHHOereewo
"pL gg | O.SN CES a bt 8/9 OOD E50 000 Bo 8 Oo OO 8 OL ee nee One Fe ea eae ee ie ee ee
IAA AMOAMD HO AMIAIAANDAOOCAAAARD OIA OMAR DADO MH AIO HE ISM ADIOSTHIOOME A
ODNDODODNDOE MAE AALC RANE DODOHDANADNHNOHSEAMDODONHDDAC HOME NE ODOM MDO
‘sny WAOAIOARGOADMAOOADADIOONPOAHDOWDDAHAADNS HOH MOM MONO HOE 10 10 OO HH
DWDAMWOAHDHWORDBMON AAHENCONMONNEF DAL MH OCADMDAWOHABDSCDOONNSDONCOCSHAroOw’w
SHO HT HD Sh CFU HD HD OD VE OV HOD NAH CT NOD AV 4 ON 6D 09 09 CD HH AD HH IG CAE OT rd HAG SH 4 OD HEI HCD
FPOADHHOE MO DRADAOMHAAHMDMON DH SASH NH SME SBHSOEAOAKRGAADOKMDAHOWOE IO
MAOAMDAMOHAMATDHAHMHOMMAANANANTNHOHAANAMHAATHADADANDEDHDOANANDAMDHWE OWS
0c 0 DON DMA HOMO ENNEDAASEMOSCOAAAMDONMNAHBMRMOSCHAMMNOFrOANSDHADHDOBDNON
1D OD 1D HOO AAO 10 HEN 0D ODE OT HID OD HA TA AA I 09 09 HAD HH EG ODED AT AN CD OID HOO VIO CO oH
12 OHNE ONMOMnhe oO DE-NVOADDONHNMNOCOCOAL-DADNHDeADNDOMArOAMrNOAHONHA
* ODOR AA HO AH ACD HD ID AA HOD A HOOD OD OMA A OHA S09 HHS 10 09 HID AH AIA 20 HOD CD
a Oar dos KE DOHOEFONADDNHOHEFOMMErOMOADHOrHWDARDODARMDONNW BONHAM O DO
a Ot HOOEE HE AEOODANANNHSOHASCHSEMSHOSCGSHeEMAWADODNDDNMND
‘qoa GRRSASSISHLSSSSMSSH SAR ABSRSARSLSABABZRHSSARSHGABISABRASRSS
CAKHAASBAANACHSMAAAHAABADSDOAGAAH HAAG AIO HOAAH OOO HHO ONAE HAC
a reOmID OE DADODODDADOHRBOMHANNGDHOHONEEMOAMO~rN
ACHAAGHAAGSAHTAAAADIDAHDOHCSOAHHAOASCHAHAAr DUO MDOHOHUMHANISOWOAAS
H Tee TT eee oe LLL eee Ee
HAMA OrFADRBOHnAD WOOF DHOANDMAHOMADRBONADHNHOr-ARBOR oo
sy DOD NDDDODDDDODDDDODDDOHODDHDDDDDHDDNDDDDDHDNDDDODWDDOHDDDDODDNDDDMODHOO
BHAA R MANA AANA AAA NA

 
ETO. 271

FITZGERALD ON RAINFALL,

TABLE No. 1—Continued.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MAMDAHRANAGOEPENHR AND Se 2
*IvOX Se a eS ee eee e SS
PAG HODONDADOBWOHOWOR =
oNtIod | YRSBSIRGSRSBIGGSSES x x
a
Cb mA tHOMMNONDODOOM = 2
26g) = ee ee ee eee a 2
AOW MOH MAD AA Hodis a dics g 3
ma
DANDHMOE ATE ANMOM Ord a o
SRONE | SIS 6g NS OEE Sure Se Printer ey ee a iss
AGQAO-OATHAHDONHADOHA x “
wo
ADMRAOOHOOMHrONAWMDO = x
5 6 Mei oar I rtp ee eens he ~ 2
FBADOSOM AAC Hides wed Id 2 oD
BAAIRMNOOALDMOWMWOaE oy 1
adage ee ee ee a 2
ADMOANAAH ASH ARG wed 2 cry
>
DOALOOErratornHMonra S a
Br ar ra ia eco tal oe gee iS &
COMNABOOANHOWE OOM dow a ot
CHODMAANHHMSAMNDNM+ iS a
SAR ee ea ey ee SS at o =
AMDGAHDOEHGWAGHABHIAAD 5 3
oO
MMOBWOAMIHENMDODDHOH 6 &
Cane) Sr See ee el ee ae ed S
APABABOrHATOHAAKAd x 3
ADHDADOROHaAANDOROVYVOD 8 a
ABTA | Se Se ee CR CO CE OS 3 eS
MOMDMOA NAICS OWI wid g oD
DOANDOM DOM OOAIMHAMHD a 2
Ty | Se eee Sole ee } 2
. DWH DGOMODAAAHHOAAAWAA s SS
o>
POL Be WowWee wen DOehYM D 2
‘re ees a 2
AWOMOWOHSCHAGHSWIOAr Is 3 x
o
AAYKOO Wo HO HHDDHWARDAD 5 o
Qf) SSS ee See eee ee o ee
MWOGAODHOOSK AM HOMO 5 8
SYARNMDHMSDHNNYWEDOAD ber ©
See et eee ee ee eee eee ne ee si o
MOG Ado WW Gis odd AS g 3
a Re Ia). te Pay ath athe Re BID ae ae these a a
MIDOMOGSOAASHOOrODGSN 3
3 SREELE SES SASSER SES 3 S
bo GD 00 60 09 GO 00.0 0.0 0 DW HO 8
RNA RANA AAA a

 

 

 

 

 

 

* Hall’s gauge was 18 inches high, 12 inches diameter, and located 90 feet above tide-

The snow was melted and measured.
+ The Sewer and Water-Works gauges are 14.85 inches diameter, and the collections are

marsh,
weighed,
‘6st ‘Aavnuee 03 ‘oggt ‘Arenuve “qBno1oq}se, pur wieySarurerg ‘6st ‘Arenuel oy ‘FEgT ‘Arenuee

“eggr ‘Arenuve
-TNOG “g,8T ‘tequrooeq 07 oungr puv ‘ToJULTYdoH pue YSno10q4s90M ‘QLET ‘JEQuIeDeq 0} T1Idy WIM “aJeNATTION ORCT ‘OLRT ‘taqumedaq 04 ‘gust ‘Arenave

‘puLlysy pue wvysarmedg

‘Ysnoloqyynog pure weyfatmerg Fegt ‘Arenurpe oF
“doquTydoH pur qsnoI0gQyseM ‘YINosoqieM ‘qIno10qyy nog ‘Mey Zururesg ‘eget ‘Arenuee 07 ‘1ST ‘Aequieseq ‘YySnosoqiaey pur YSno10q

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

oO 008°S% | 08°ceL | 00°8s 96° 6F OF LG OL'GF | 90°9F] QS°EF, FI'LF) BLE} 6E°6E | LUFF | 81'8e : GF IF 66° Lg CO FP 99° 6F 6F SF |*Te}OL

&

i |

= OTL'E 98°6¢ Te's F's 68°9 88° L6°F | GL°S | LIS | ge'g 08% 96°S £8°% "ae Le"9 18°0 69°€ 60

H LOT F TL°s9 0@'T 66°9 Sob L9°% 99°F | 60°9 | $9°S | I8°T STT 60°F 6L°T 89° COL 08°¢ 9L°9 €3'°P

H Slt F | 09°OL 19°01 90°F 66°F £8°S €@°S | OLS | 8F°S | 09'S Ls £6°S FL'S 18°0 Cro 6S°8 FOS 68°F

< GEG Th 19 00°9 09°F 8a°8 GE" 16'S | GFT | 98°0 | eo°L FL'8 69% 09°T 88°T 66° T 6e°0 C9o'F Shs

ey LOOP | 69 LO 98° 8L'> 6o'9 86'S OL'F | 8l'L | S9°F | FLO LOT 98°T 10°F qg'9 69 89°8 LT eg°¢

zi F8L's 99°09 9F 6°83 Te OLS 96°S | FT | LOS | 89% LUT ges L6°9 6° L6°% S6°S el'6 Log

< 986°S OL LE £0°S 08°% FS G9°S LET | L8°% | FHS | OF'G 99T 6E°9 FILS 6L°E 88°¢ CPS FOS Fo'9

fae} €06°¢ go" Tg | T's 76% 68°F LUT 66°% | 6F'S | LES | 6T'F 90°9 19°€ F8'T 8o°T 96°0 OL’e 9L°S 99 §
OcE € SI's $9°S IP's Shs 96°F 66°% | 09 & | OFF | FBT GAT 007% Ole CLF 6L°g PFS O0G'F B'S

w 8L9°F 9G" Eh ehh LES 60°9 06°F T9°S | LOT | GL°F | 8L°T G9°S eho 16° FL 69°F 98°8 Shik PLS

oO 90°F 66°F9 19's g9o°T 89°S 8LF 8°9 | L8°€ | Sg°9 | 98°S go'F So'F 86'S 99° L6°9 FL'0 10°F SL's
6LL F L8°99 89'S LE*G SUP 06'S 96°9 | TL’F | 80°9 | 18°S 96°39 99 9 LoS BFS s9°9 Go's €8°T CHS

Aa o

4 q 5

< NVI | ‘“IVLOL,

i “068T “6881 “8881 “L88T | “988T | “S88T | “PS8T | “E88T | “8st “1881 “O8sT 6L8T “SL8T “LL8T “OLST “QLST

o “06-SL8T

N

&

Hw

iy

‘prvog dayeMy Jo sytodey [wnuuy WorIy ‘OG-LEST IOF puv “4Qysnoxrq jo suLy, ut

Aypoedey wo ‘yg9q ‘Avy Jo ytoday Tetoodg woz ‘9g-G/9T OF USZVY,

272

“SOOB[ [BIOADG 4B SUOTPVATOSYO JO SUBOT\[— "ALON

‘SUVEA NUTLXIG—GHHG-UELVA, ABATY AWOGGAg—“TIVANIVYT

6 ON WIV
273

FITZGERALD ON RAINFALL, ETC.

 

 

 

 

 

 

 

L9°GS | OVENS 66°98 90° 6% Sugg €6° FZ | B8°SS} B6°ST| 8L°S| GL°TT] OTST 99°06 SST LL8T | 6F 08 6F° SS 16°83 GP'0% | TROL
S6°T 9T Te SLT 00°F Fe sT'T G8°T | 60°S | SO°L ; FEO | 99°0 8é°T 1é°0 78°70 08°% 18°0 FO'T [°° * 99
to'L F6°9C, Ors ges 9L't #90 9T°T | €0°% | 08'0 | SE°0 9¢°0 89°0 gs°0 se°0 Ste 88°T SoG | AON
core 8691 SOF 61'S Lo" E°0 96°0 | 09°0 { STO | E8°0 £¢°0 €6°0 8T'0 sto Sit CFO SUT |°°"°°990
9F'O Se°h 6L°0 GFT 66°T 61°0 02°0 | T%°0 | 80°0 | 9T'0 €¢°0 60 Fra Fo'0 oro te°0 98°0 |°**"9deg
ga'0 BRS £2°0 oaG 89°0 88°0 LT°0 | &F°O | 9F°0 | FIO Oto 92°0 160 aL'o 60 oL'0 Tho [any
FEO 6g°9 6T°0 &U'T 16°0 0z°0. 120 | IT°O | OF°O | 12°0 STO 6F°0 1g°0 RO 980 ee°0 4g°0 [°° 4tme
18°0 96° ST 86°0 eUt £1°0 TL'0 gO | &L°0 | a0 | 2g°0 16°0 Ths 0s°0 ILO s0'L 880 og'T |*** oun
10°% 61k FS Lo°T 16°S 08°T 86°T | 88°S | F8°T | LOT O° CLT 6°0 66°T Bhs £0°S BUS 0" ARIAL
c9'$ 96° LG FBS £F'S Lo} CaF 9e°€ | STS | 76°F | SES ost LS 60°S 889 elt g9°¢ 96°g [ot ady
0°S 18°08 os’9 68'S 8L°9 alg LO°S | ORT | SL°9 | LBS 90°¢ FLL SF's Olt 6o°8 16h 98°G [°° 4B
8l'é 68°09 OFS £6°T Sas 99°F €L°L | 81'S | FLF | 99°T La°E 6F'S 86'S 94° 6S°T 80°% 1h "8" Qed
COG T8°ts. IOS 96°F 88°T 69°F 19°% | 00'S | LL*T | 09°0 16° FL‘0 00°% SOT LUT StT sto jc" aee
‘NVaN | “IVLOI,
“O68T “688T “888T “LEST | “9881 | “S88T | “F88T | “E88L | “T88T “TS8T “O88T “6L8T “SL8T “LL8T “OL8T “CL8T

 

 

 

“06-EL8T

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

‘daLOaTIO“/N TIVANIVY SHHONT—SuUVaX NEGLXIG—HiIddaqd dO SHHONT NI GHHQ-UaIVA, UMA AUNAGAG AHL AO atarx

6 ON WIGVE
FITZGERALD ON RAINFALL, ETO.

274

‘omyy Surpuodseii09 of} Loy [[eyurer pozeinqe} oy} £q

Surpratp &q ‘omen omes oy} Jo sqUOUT UeE]XIs Yous soy pu ‘reek Jove IOZ ‘q}UOUT Yous AO} ‘preté poye[nqey wWoIy poureyqo syuerjonb ere oaoqy

 

 

 

 

 

 

 

 

 

 

9° 6F hae | 6°09 G89 B39 L°99 | Q'6F | FSF | FOG | TFS] 6':OF 9° 9F 6°18 S°oF 9°e9 6°19 Gt 6 FF | Teva
gto ges SLOT | 9°00T | 9°6%@ | 9°98 | 8°9L | BIE | 9°6 FFs 6° FE OIL 0°6T 0°68 F'F9G | ESS

9°6E L'PLT | €'eg 6°99 RSG | OSB | ESE | SIL | S'6T | FTE 9°9T 9°6L GST OTF G GF 9° CE

T'S@ 9°8E 9°Ts PIL OCI | O'S | 81T] 09 | 6's 9°SB VIL 8F 9°ST ST @°8L 9°8I

& PT GST 6°08 GEG ST | OL | Lt] #6 | GOT} 19 o's L'°8 6°3L GTZ 6°If 6°9

0'éT v9 o°19 6°OL ob ly | 09 | 66 | OEE] O'9 T'6L ag 8°0T Gr 6°9 O° OF

68 SL 9°OT 6°t1 rg F'9 | LL | GOL | BL 3°38 6°02 6'F TL Lk GUL 9°€

1°66 €'8F £'0F L°8% 6°93 | 6'SG | 9°9% | 60 | LIS] LFS 8°GP OF 8°8T 2°03 OF 8°8T

€°29 8°9F €°€9 €°09 Q'FOT | L°Gh | 8°89 | O'S9 | 66S | FSF 0°6F Tog 8°98T | G'09% | O'L9 ge 96g | Ae
T*60T S Col | FTL €°88T | O°901 | OTST) 8°98 | L'LIT| E'9ZT] 3°28 gest | 1°s9 I'FIL | 98h OGL | FSET] 6°79L | ady
9°60T 0°%8 6°00T | 6°S6 F'FOT | L° TOT) L°193] OFT] BI9T] O'IGT | 9°FZL | O'FL 6°08 PeeT | LOL! G°90T | G9, | ae
G°8L SOL POTL | 8°88 £96 | LSet] P99 | FUL | 6ZF] T'S8 9°e9 6°FL PLL 9°99 6°90 | G'F9 QOL [°°""qar
T'6F ¥'83 ¥°S6 €°oF 8°88) | OTF | LF | SFE | FIT] TL €'ét T'9g ¥'0S eLg g°9E Leo ob “uer
“NVA

“068T “688T “8881 “LEST | “988T | “S88T | ‘F88I | “ES88T | “SST “TS8T “0881 “6L8T “BL8T “LL8T “9L8T “GLST
“06-SL8T

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

"prvog 1078 A\ Woysog Jo sytodoy woary potdoo ore sorn3y “QG-L8BT PUB ‘61-GLET SIveL OT} IO,g—"aLON

‘SUVaX NAALXIG—dgHOQ-YRLV A AAAI AUOGGNG—GaLOATIO“/N TITVANIVY JO AOVINGOUaT

7 ON WTAVE
ETC. 275

FITZGERALD ON RAINFALL,

SUOT}VAIOSGO WOT O1B BIOQUINU posieysay

“IJOAIOSY [ITH JWUySeqO JO

“sUOT}RAIOSGO JO STRATTON} WOIy AT}YSTIS AOA LAVA 07 Sv Poisn(pe Os ‘MOLJeIOdeAS WHOUT JO GAIND TOIT x

 

 

   

 

 

 

 

 

 

 

ozce | a'zz9 || so'se | o9'se | I9°TF] O8'0F | 9°EF 2o'6e sor | Loop | gue | 2679 | goveg [ort cette on,
I9°t | 91% 1o'te | Ig9'te | Totte | T9'Te | T9*Tx 19° Tx Tote | Tote | Tote | Tote | To'Te footers ters ress raqureved
ez'z | Foon || set | te | oe | 69°% | €2°te 80" 09's | S2'ee | SoG | Sete) g9%O [osessert sms eeeess
9.-¢ | egog || ete | see | Ts | ete | ons TI'Ss 6L'% | 662 | 9's | T9°% | ate |:
sue | sesy || sos | tee | zoe | soF | erg 00 F 70's | ose | Foe | SOF | BFE |*
ose | sour || sar | Teo | O79 | o8g | IF 09° Sx res | sag | eee | OFF | T39
geo | aes6 || Fors | 2979 | 9679 | 6g7e | GOL 86°Sx ws | te9 | Fo'9 | e8'F | oth |°
too | ooras || zee | g6'9 | sog | gz'9 | Ton oo" Sx gp9 | zea | 9279 | g9g | Fg |:
ore | cpt, || use | gee | see | ore | une OF Fe zg | 68¢ | FF | GOP | oF Fe |
woz | u¢2F || ez | sez | Love | ate | 86cte 86° Ce 86'te | 86° | 86x | 86% | B6'Se |
On'T | o'2e || ObtTe | OTe | OLTe | OTe | OL Te OL Tx OLTe | OL'Te | OL'Te | OL'T* | OL'Tx |" ores
cot | ogot || gots | go°Te | 90'Te | $0°Te | 0°Ts 90° Tx GO'Tx | ¢O°Tx | $O°Tx | go'Tx | So°Ts |" srenaqed
96°0 | 9¢°ST || 96°0% | 96°0« | 9670 | 96°Oe | 96°0x 96" 0x 96°0x | 96°0x | 96°0« | 96°Ox | 96°Ox | trees sees Arena p
“MVEL | “FVEOR|| j ‘ : é FS-TsgT paw] : ; ‘ ;
esst | ‘aast | ‘eset | ‘oget | “sest | *5,o ole, | “osst | “6zst | “Sigt | “LUST | “OLST
“06-SLSE

 

 

 

 

 

 

 

 

 

 

 

 

 

‘SUVEX NAALXIQG—SHHONT NI DOVTNNG YALVAA WOU NOLLVHOdVAL

‘¢ ‘ON WIAVL
276

TABLE No. 6.

YIELD OF THE SuDBURY RivER WaTER-SHED In Munions or GatLons—SrixTEEN YEARS.

FITZGERALD ON RAINFALL, ETC.

1875-90,

MEAN.

H
10
a

446.20
729.99
604.42

 

 

Toran.

7 139.16
11 679.89

18 384.80] 1 149.05
9 670.70

 

 

1890,

|

5 296.5]| 21 451.70] 1 340.73

ao
oN
oo
=
cr
ant

So
es
wa
o~
Or
oot
HO
co.
wo

2.0)}106 440.70) 6
29.1;) 76 928.50] 4 808.03

85.4) 42 305.50] 2 644.09

2

1

9!
280 8
250.0
306.9

AADMA
AMO HO

 

1889.

COHMADMDON

57.7) 1 031.6

867.5
378.8) 2 740.1|| 34 363.90] 2 147.74

223.7) 2 321.6') 41 214.10! 2 575 88

OAMNMAANMAA MIO

 

1888,

AMID DIDO CODD

 

1887.

 

1886,

 

1885.

 

NOHOSHae
AN OD HOD aang

 

1884,

ARMM OWMOMNDMS
Serrsa-Knanes
BANDOBARRAGI
NOADWHASOD AO

AOOON a

 

1883.

QMO OAR AAM

 

1882,

AwWoOnNO Ss

 

1881.

AQOMODNIARCOA
Sigg Suzgyans
sce e eae soe

AADANOOM WHO

AACA OD

 

1880.

CHNOOREAH

246.5
481.7
424.8) 1

 

1879.

 

1878.

mawco wo

375.1

 

1877,

4

5

8

3

3

1
29.9] 1 146.3

139.0
1 522.4] 1 244.3

 

1876.

-1) 3 108.9) 7 658.8] 1

.8! 3 307.3) 3 949.0

 

¥*1875.

 

 

 

 

 

 

Total/27 593.7/32 309.9/34 444,8/41 202.0/25 528 9/16 561.6)/26 818.028 656.5/14 620.5/31 084.1/24 718.4/29 831.7/31 663.5'46 717.337 971.0/35 277.4]/480 057.25130 003.58

 

 

1879-80, 78.238 square miles; 1881-90, 75.199 square miles.

1875-78, 77.764 square miles;

* Area of water-shed
ETC. 277

FITZGERALD ON RAINFALL,

“soryu orenbs 6619) ‘O6-188T

‘soflur erenbs gé%'s. ‘OS-6L8T

*sojtur orunbs FOL"LL ‘SL-SL8T :POUS-19}eA\ JO VOIY x

 

 

 

 

 

 

 

 

 

 

OT Let | crt" F9°OFL | 96°O9T | GF'LET | G2°FET oF 9¢1\8b" FOT TP TSl|86°T9 | 8c°OOT | €6°EIT | TOOL GZ°SOT | SO°FLT | TOOFT | 69°9ET | LEO'OTT |* Geol
GL°09% | TO'FSE | S8°FL |SO°STI\69°9ET/T9°LOT/I9°SS | 19°98 | 81°06 1% 1% 66°S¢ 9G°8E | LI“SST | 99°49 FOL
RSET | O6°OTE | BB TF |ZERL |OV'LEL|GE' OS |T8°Es | 98° FS £6°SF FR FG 88° FS L9°€0G | LG OLT | 68°OST | 89°9ST
GL'StT | 29 EG | GL'%S |LG'9T |90°6E |L9°G [29 1% | 28° FE 69°16 0§ @L 99 8 OL°s9 86°9L OL’ 8% PL LL
18°S6 FE'FEL | I6°SL [MO EL SO FT |LI'Y |Z9°OT | 99 SE 6° Ge CL'6 €0°LT Se 6L “uh 61°CG 96° t%
19°99T | ST FF €6° FS |S6'OL |96°L% |L8°6% |FL'6 £F'9 6° LT 8° F1 €8 LF Te" Lg LoFL 9L°8P 19° LP
GL°EL 99°€T 9E°ST |9FET [2° L J€0°9% |GET | FOOT 91°78 Sets 0°61 SPST 96° FS 0° 3s, L9°8€
66°SL 0 6F 60°8F |€9° FS jS9'6F [EF SF 16 FE | FST F9' SST | €6°1% 40°09 £8°09 8° TL 69° 9% £9" FOL
L61EL ‘GF ILLG || 66°89T | €€°ZOT | €6°68T |} LE "LTT [ORS FF" SCT 68° 61T:L0° 601 84° 0ST | 82°SIT | F2°t9 €8 FET | SL°L9T | TF'LOT | S6°9ET | 06°CFT
LO LTS SO'FOL | LL°LOS | O8 FUE [FS-9CC/GT 116,00 FEL ZO'LST| Z6°OOT | S8°GLT | LF IFT | O@'LLE | E9°S6E | OO'88s | TT°96E | 987998
£0 GEE EL SST | OL'9L8 | LOSS | 1S" 6ES/C6 C8 CF OFFIIF 181 0g 0s | S8'SuF | TE'99l | 90°Z8Z | 96'IZF | LI-GLE | O9'EES | IO GGT
FH OCS IL'6EL | €6°90G | EL 6k [LE RSSiFS LST F9'OGR ST" OCT 9° GLZ | 68°6LT | IS°91Z | OL LO% | B9°96% | TZ FIL | LO°FOT | 20°O8T
GU'SEL |TR'TOLG || FO'STT | GL°ESE | SS°ZST | 9B 10E |96°G9T|LO' SFI GL SIT 96°8E | CE FFL | 9S" SF 99°SéT | 9L°F8 GL LIZ | 00°6L 88° LL 86°3L
‘NVaWW | “wag
“O68T “688T “888T “L88T | “9881 | “SE8T | “F8ST | “E88T | “Zs8T “T88T “088T “6L8T “8L8T “LLST “OL8ST | “SL8Tx
“06-SL8T

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

‘SUVA NAALXIQ—aNOOEG Wad LHaY OIdOO NI GaHQ-YaLVA YAATY AUOGGAG FHL AO ATAIZ

L

‘ON WIV
FITZGERALD ON RAINFALL, ETC.

248

 

 

| |

FIG'E68 |929°G0E 9 ||TZT" 69F/0F6'F0S| 6s" 129/90" IZF|E0L 968 90L*8ZE 89E "ELF FCF FET|S89 FIE|S6E" LSE|789° LTZ|86%S" 9ZE/E8" 67S|6E6'GFF|LOF “STF OF8" PGE) "°°" [BIOL

 

O*8"SE | TIF TFG TL8°08 |99F'69 |1ZE"F6 |Sh6°6T |ST9°Is |e6e'9e |TLO"Sz |666's $9L°6 |800°F% |62F°9 |6EE"FT |18F°86 |6L6°68 |LGO°FT {L60°8T |*** tequiaoeq
SLT°83 [FF8"094 SEF 9E [62589 |SFL°78 jLGO'IL le6t"0z |FzE'se locz-g leet’ 18G'9 [8F8"IT |9ST"9 J99T'9 [@BL"09 \OEg'ZF |se9°ce |L90°6E |*** *ZoquTosoNT
189°LT | 106°Z8% SEP°0L |ZEL'8E 1896°19 je68°9 |LI9'F [90F OT [LLG°S |T9L‘9 8L0°6 j2Gh"9 |OST'S |T6T'% 'Zo0'9T |ZL9°6L |OFG'L |6z0°0% |°°****x8q0390
@86°L = |S0L° LET SIL "EL |FOL' FS /OF9'FE |6s8'S ez |zeo'e Igte't |sen's leet 916"S |80F°S j1zo'F [ess'F [LLL |zeo's |Tss°9 | ***‘aequteydog
GL9°6 —-|96T" SST T80°F |O6E'FF /E9LIT |179°9 |LI6'S jost'L lege'n cers FIL'T j069°F /F89°S [LFG'SL [IPL FE [FoL'S Je9g°sr |ggz-et |
cg8"9 = |FE9°S6 908"e |1F9°6E |se9's [sage losses lpze'rt |se6'9 loxg'e FLO'E |899°8 |LOP'G |8L8'F [66'S |IGz°9 |zL9°9 |z96'6 | °°
960°9T 99° TF GE0"LE /S69°GL |FF9°GT |TOP'SE [e60°9 |oLn zr |L8F-ZL |TO0'6 698°ST |OST'OF |29G'9 'TOF'SE |€L1'ST [FIG "LT [¢S9'9 [e60'9e |°*
969°FE /LEL'Sgg 098 GF |S9%"LZ |F09°09 |TL'Te 6zE'ss |91F'1F leFE' TS |T90°6e 6£0'OF |9T6°6% /8E6°ST (609° Fe |xzo'eF |FETeF j98%'Se l618-98 |-

096°G9 /90%°L00 T |/6€%'99 |g6e'eF |9ge°6L lo6osL |zTF-g8¢ E949 |F09"SR |L8F'OF |Z70'9% |ose'gF |evo'ce lost'e6 |6LL°SF leog'TL |99L°86 \ZLF- 16) |""*"
L0G'L8 |€E9°S6E T |/8G6'ZIT|Ech' IF |99"O0T\E06'88 ST8"E9 |OFL'SF |9FE"LIT/ES6'6F |C00'8S [GIT F3I|Z69°F (LES SL |6LL'SOT CBG OFLISF LET/6GL 6F |*
00%°So |T0%" E88 ST8°OF |LLP'ES |799°99 [O1G"6L |TeFTSTILIG'LE |Z1F Ze |s16°8t G6G"LO |F6Z"EF |€ZB"TS |F06 LF |8c0°69 |O89"9z |S99°6e |FE8°TF |° Arenaqge,T
8E9°SE |F0Z"OL9 €88°8E |19Z°98 |SF9°ZE |190°08 |F83'SF |8LZ'8E loSs"os |6LE ‘OT T9F'SE |LEB°ST |FIL'FE |GOL"TS |860°99 |L0F°0% \9R6'6T [este |°****’Aaenuee

 

     

 

‘Nva | "TvZOL

 

“O68T | “688T | "888T | *L88T “9881 “S88T | “F88T | “S88T | “28st | “1881 | ‘osst | ‘exer | ‘suet | ‘nest | “9L8T “OL8T

 

 

“06-SL8T

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

‘SUVA NEEIXIQ—ATA ALVA Utd SNOTIVY) FO SNOITH NI GaHHg-YaLY AL WGAIY AWAGGAG GHL JO aTaI_

‘8 ON WIV
ETC. 279

FITZGERALD ON RAINFALL,

 

 

 

 

 

 

 

699°T veeee" 1) 686°T | OFL'S | 929°G | SBL'T [B89°T |Sse"T |LFL TL |F08'O | FEEL | QT9°T | S68°O | E8E"L | OFS | BLB’T | OOL'T | FOGLE |**tavoW
689°T | FG0°LZ || TST | LOPS | BOL"F | G66°O |8L9 T |9T8°T |TeF°T |660°0 | L8F°O | GEIL | TLZ°O | 9TL'O | 9T6'F | 966°T | BOLO

SPT | GSG°SG || GLB"L | 00'S | LIVF | OLG'O |IFO'T ZBL |1LZ°0 |L18"0 | FEO | TI9°O | BIg"O | BIE'O | 619% | GELS | E89'T

Z88°O | O@L'FT || ST9°S | UG'T | S60°S | F6Z'O |SZZ"O |6TS‘'O |6ZL°O |88Z'0 | E9F°O | L8Z°O | LEL°O | GOT'O | 66L°0 | LL6°O | T9E"O

G1#'0 | 989°9 80L°0 | FLET | 98L°T | GLTO j(@8T°O |L8L°O 890°O |T#I 0 | FLF'O | GOE'O | FZI'O | BIZ‘O | GtZ'O | Z60°0 | SE8z°0

BLPO | 979 L F000 =| YTG'S | L8Q°O | TEE'O |9FT"O /ZLE°O |LEE 0 [%ZT"O | 980°0 | 62G°0 | F81°O | 119°0 | 9EL'0 | LBT°O | LZ9°0

G60 | €L9°F 99T°O | 086°O | Z8T°O | BLT°O |6LT°O /960'°O |9FE°0 |SLT‘O | EEL°O | 8%F'O | E120 | EFz°0 | GBI'O | ZTE'O | E8z°0

6LL°O |} 9SF°SL || 8L8°O | TIO'L |} G99°O | OF9°O |FIE'O |699°0 |FF9°0 |#9F°O | 8T8°O | OLO'S | TLz°0 | OF9'0 | ZBL°O | ta6'0 | EFE'O

TELL | LOL'LZ || FILS | TOE'L | 989°S | TOG'L [FILL |290°S |t69 LT jOSF'T | 866°T | S6F T | 964°0 | esL'T | BGT'S | Ets | ToL'T

L¥G'& | 9FG'TG || 006°S | ZBL | 60°F | SOF [ElO'E 8U8'S /G1F'F |880°S | GFE" | TEES | 8O8'L | 128° | 919°% | FOL" | T60°S

Foe F | LEV'GOI {| 9E9°9 | 1L0°S | GOOG | LEFF [CST |keF°S /2g8"S |c6F°S | GOEF | S69 | 9ZT'% | SON'S | BFS | BFE'L | Z98°9

£20'S srress Ti gos"G | OST | TlO'S | LLE'H j8ZF'L |S6O°S |LEE"F [869° | SIL" | GEES | SOL'% | LF9°S | FIB'S | GOF'L | OIT'S

GLL'T | GSF'8S |) TFET SOS'F | 629'T | 900°F [09G°S |O1G'T |OFS'T /8T9°O | OZ6°T | GFO'O | SEL'T | e8o'L | 008°s | 6BIO'L | S66°0

“NVI “wag

“0S8T “688T “888T “L88T | “O88T | “S88T | “F88T | “E88T | “S88T “TSB “088T “6L8T “8L8T “LL8T “9L8T “QL81
“06-SL8T

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

‘SUVEA NALXIS—TUAL Huavoog wid GNOOEG Wad LAT OIdO(t) NI GHHQ-YaLVAA UPA AUNGGAG AHL dO GIGIX

6 ON WIAVL
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

£L8°%6E|896" LT 9]|6TL' 69F|EE6"FOS| SFL 1Z9|9ZO" 1ZF/909 FEE|LEG"LZE|Z69“GIF|9TF S61 |e99"ETe]/ GOL’ 9¢¢|869°O1Z]689 ETE] TSI LUS|6ee"SEF/996 “TIF|OLL Tse) ~*"* * Te9OL
-  oFg'ge |oer1F9 ||TL8"0e [egF'69 |FTE"F6 |T96"6T |L99°Te |e9e'98 |OTS'S% |996°9 |8LL°6 /SEL'FZ je99"9 |LOG'PT |Fee'S6 /S0G'6e /66E' FT /EL9°LT
S nz 8z joe cay |\BeF-98 [ee"89 |ThL'e |THO'IT |L9G'0G |GOF'9e [TLZ"9 |g00°9 jeFL'9 |186° TT JF00'9 |T8T°9 |8LG'19 |oc8 "oF jOBF’ee [aT Ge
Fi «694 LT (26z'F82 || eeF'OL \eeT “se [sL6°T9 je6s's |69e"F |s6F-OT |cog's je60'9 |LFT"G |R69°S JzG'E |s68°T |AOS'9T |FIB'OG |T16°9 [LAT OG

LGL'L |9GL°F2L ||STL"eT [ZOL'Fs jLES"FE |I8e's |gcz'e jFOF Ss |S9T'E |L9e'S 0096 JoFL 9 [GLT'S |996°E |TLO"F [OF8°O |oRL'G |FFG'S
~ 26876 jore-o9t ||Ig0'F |oTF'FF |FOL'IT |6F9°9 |T89°s |8TF'L |g68"h |ees'T J6Fe°"L |suZ°F loess |Lee°ST [FOL yT joTg'# /Tes'1T |S60°OT
F — no9'9 [etL68 |leze's [aro'er joco'e feca'e |tuc-e feco'T [e6L'9 [ace's [6IFG /618's |8LF 9 [6RE'F /860'S j090's | [6T0'8 ZLL'6
Z —«GOL"FT ]Pos'9ge |[ee0 LT [F89°6T [LI9°GE fe6e'st |o09's |u9g°ZT [LcE'’T [98'S |LEO'ST /T10'OF [006"F [900°eT |coe"FT JO9L OT [1k9 2 ¢18 "St
i Fea'FE [FOL SS |lace'ZF JOGG"LZ |L69°09 /LEG“TE [S10 Gs |TZE'Th |OLL'TE |696"87 |196 "GE /ORL"6G |HED"ST /OTF CE |SOL "TF |6LE'GF [967 "FE [9TO'9F
, £19 29 |918"T00 T]|6ee99 |T6a°CF |see"6L |6L9°BL |LG6°LS JOCE-Fs |8OF'98 [96G"OF |FLE'SC |99T "OF |0G6 FE |GFO' SG |GLL"SF |FES°OL |e8e'L6 |FFT "NS
AZ —-gz0°L8 |9LE"Z6E T||826 "GIT IGF TF |196"OOT/REB "88 |169°E9 |LE'SP |FSL"LTI|C6L GF [994° LB |6FG"SCT|FES "ZF JGT "CL |898"LOT/STL SFI/G16 9ET|STS" OF
“2 - 861°S9 |TOT“ess |leTs'aF leu se |LGS°99 |T8T'6L |T6Z"FET/OFG'LE |SGF°CS |ETO 6% |89G°L9 |C6E"EF |BIB"TS |LLE'LF |LL0°69 /960'9G |S68"6E [218° IF
me «gabe |go9-eug |legs"se /6F3'98 |se9-ce [T9z°08 |F2"SF |FLE'Ss |SZT'Te [SOS NT |T99°SE |FOS"ET [O9L "FE [TSLIG |LLF-9G |€69°0% /Z98"6T |87s"s
Z
° “NYS | ‘IVLOL
a ‘ost | “osst | ‘sest | ‘zest | “geet | “eset | “F88T | “egsT | “e8xT | “T88T | “OS8T | “LST | “SL8T | “LL8T | 9L8T | “SLBT
4 “o6rg!
a 06-SLAT
a
<3]
&
nm “gud zed p@ A[rVeU pUYy ‘syZUOM yuerOyTp ur AT}WST[Ts Surdava ‘-4u00 tod Fg yoge svar TE-NGST UE 9OBPING 104V\\— "ALON
& :
&

280

‘SHVEX NUWLXIG—TUP[ TUVAOG Ud SNOTIVH) JO SNOITO] NI
‘T6-0G8T 10 HOVIUAG YALVAA ANV CNV] HHL JO sIsvVg HL NO GHHQ-UGLYM UAAIY AMAGGNG FHL FO ATAIK AALWIAOTV/)

‘OL “ON ATAVL
ETC. 281

FITZGERALD ON RAINFALL,

 

 

 

 

      

 

 

 

ILO'ZOF|SEL ELF 9} |Z" LLF|GOG *ZIS|GSP 19]096  FEF|OLT  SOF|OSF’ GEE] LEZ" SGF| PFO FOZ) IBF FZE/BIT“ 99E|GEE G1Z|O9O “FEE|S7E “EES/ILL SFFIGLG GLF|ZLO" GSE)" TROL
989°SE |86°8E9 ||FFIGZ |668°OL |09S°S6 [04° GT GS9°OS |8B8°9E |G69°LZ |OFE'S [CFOS |Z6F'SS |8S6°F |OGE™ST |0T8'8G6 [96 OF [ITI ET |9E9'ST |" "** Lequraoeq
QSL'8Z |GLT'O9F |/ZEE°SE |UGI"LE |O68"ZS |SZ9" IT \GLL GT |S6% FE |€0C'G [699 |ETO'L JTL IL |LOL 9 |EZI°9 |TOT‘OS /E9l ZF jGcg° le |6h6"8E |" ""**** JoqQUIOAON
OS9'LT |8L0°G8S ||/S6F'S9 |LLL"8E |LLO°E9 |8S9°9 |FEO'S I€8F°6 |896°% j9I8"F |O80'OT |986 2 |98L°S |B9G'S JOFE'ST |GFE LT |€L9°L jZEB EI |°* °° > 777" 4eq0200
BBG°S |SIS LET |ISZL'SC [IPI FS |LTO'SES |SOF'S [SLE'F [VGL"9 J|OLT'E |GZO"F [SSL |BLB°9 [289K |BEZ"9 [989 |6LN'E [69° |669°9 [°°
GBF'OL |GIL LOL |/10G'9 /T66°SF |LOG LE |6GF°L j16L°S |608"L |649°8 |ZI8°F [069° |006°9 |9LF'F j96G'IT |LGTFT |990°F |LOG FL |FOF GT |**
GPCL [990° FIL |/F8S°S [696 LT |88e°9 |¢<TO'S |TOS*t !8ZI°g |6Eh'8 |EsF'S |890°9 |OZB"OT FEE" |1G0°9 |910°9 |966°9 |cEo°9 |096°OT |"
6S8'°9T |8EL°69 |/S6L'GL |FL6°0% |QLI'SE |ZOE FL |SIT°S |ZS9°ST |ZSO'FT |GFO°IT |19G"ST [STO LF |FoL"L j69E"SL \6TG'ST |LFE GL |TZ6'L |998°9Z |**
89Z°9E |F82° 089 [1B8E"SF |66L 6% |FAF'IG |TLGFE |GL9°ES |QFG' Sh JOGF'ES |SEL°OS |886°OF |LOF' TE |Z9S° BT |LIZ' LE (ELL Sh |O8O'FF JOSS "9E |FB8B°LE |" ”
969°F9 |TE9°SEO T|\SIF' 89 |GBF°SF |FEE"SS | F098 |ZE9"OY |FLB"SE EES LB [SUS BF [PsP LZ |6LE'SF |8LO'9E [79° C6 |LLL’ BF |6E0°EL |09G OOT/GFT€6 | °°
TIES |FR6°ZIF T|/80% ETL |SE9 ZF |TFSTOL/990°06 |ESL°t9 |TTL'O9 [SUP ELI I6LF' TS |LFZ°06 j9G8"SZT|8E0" EF |689°CL |FI8 "601/898 GFI/ITZ 8ET/G00"09 |" *"" "Wore
LEZ'EG |LOL"F88 | |STS°BF |GLZ°FE |SE6"9G |T89°GL 908° SET/LGG'LE |000°S8 |61E°8S |S6F LO |62L° ZF |6F8° LO |FGO'SF |60L°89 |S6T LZ |TLE"GE |L66°TF |"* + Areniqag
Z80'SE j|SO0S' 199 |/06B°6E |989°98 |O98"TS |T6F'0O8 |LES"Eh IGE LE |LOL “GS |9FL°G [996°9E |OLG*OT |T6E FE |689°1Z |119°S9 |ShU'O% [6G0'0G |G9L"% |" “++ kroner
“"NVGW | “TIVLOL

“OG8T | “G88T | “S88T | “LEST | “988L | “S88T | “FS8T | “EB8T | “Z88T | “IS8L | “O88I | “GST | “SL8T | “LUST | “9LST | “SL8T

“O6-GL8T

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

‘rayea fq pataaoo suotyz0d
ayy jo ppetk oq} Toy oouVAMOTL[e SuryvM Lq poyg-reye A, Toaty Ainqpng ey} jo pretf peartesqo wWo1y poonped—‘aLON

‘SUVA NTGLIXIG—SNOTIVE) JO SNOITU] NI wovadaAg GNv]T do TOL muvaAvg INQ 40 GIdIt CGALVINOTVO

‘IT ON WIAViL
ETC.

FITZGERALD ON RAINFALL,

282

 

 

 

 

 

 

 

 

 

SOL'T er €20°S PLUS 699°S FFB'T | SILL |] G8F'T | C8L°T | S980} OLE oso°T L%6"0 OTF T 196°S. 606'T SLL‘T FONT «| * WROTL
189° 106°9Z || OSF'T 669°8 SL F 696°0 | Og9°T | TF8'T 18F* GLUT L¥Z'0 CE6'F FI0'S 089°0. 0g6°0 = |*** 99d
SFT LIG°SS || LLE“L | €L6°% GLO F 009°0 | 0Z0°T | G9L°T 6980 189°0 9FE"0 L8o°@ PLI'S L69°T 600°%
088°0 | 6LO°FT || IFS | SE6°T 8tL'¢ LEO | S00 | ELF O £09°0 66¢°0 6&1°0 99L°0 968°0 €8é°0 066°0
ShP'0 G80°L LL9°0 TLO'T SOL'T 6LZ°0 | 9860 | L620 PLEO 7ss°0 | 061'0 00g °0 6S1°0 TL00 OFEO
$tG"°0 TLE’ 8 096°0 966°% 969°0 IL&"0 | G81'0 | 0680 F8L°0 | FFE'0 £66 '°0 L0L°O £06°0 FILO F690.
9¢8°0 €0L°S 613 °0 968°0 FIS'0 023°0 | 0FZ'0 ) 992°0 &S6°0. Ors "0 696°0 £930 6FE°0 190 L¥S‘O
698°0 GI6"ET || TZ0'T 680° T €8L°0 88L°0 | GIFO | 2080 LS6°0 TELS 868°0 1280 866°0 80F 0 098 T
Ost Z96°8G || S9L'% LOFT 699° SOL'T S8L'l | €FLS 9F0°S LOG*T TI6°0 92'S. 006 °6 So8'L 888'°T
Tess | POSES || ETO'S OFZ *Z 9F0'F LOL'F | BAUS | ASS LIFT S6FS 198°T 919% LOLS ILLS F08'F
80%'F | S3S'OL || OG9°9 SES €c0'9 S6bF | 76S E | 189% F09'F 08%°9 SFLS 18h 'g O8F*L 868°9 96F°S
620°S fee te 996°% F68°T LE0°s €0F'F | FOSL | GLOC 08h" 196°S 99L°S LOL’ £09°T TOTS TZ8°%
ISh'T ST0°8% || 196°T GEE" F 069°T LIO°F | L8TS | 898°L 9F8°T 8Fg'°0 OTL’T 9LL°G 000°T 000°T 8é1°0
‘Nvay | “wag
“O68T “6881 “888T “L88T | ‘988T | ‘S88T | “F88T | “E88T] “8ST “I88T. “088T “6L81 “8L8T “LL8T. “QL8T “QL8T
“06-GL8T

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

‘suvay NGALXIQ—CANONGG WEd LAD ordoy) NI GOvaNAG AGNW]T wo ToOPL quvnog aNO dO GIHIX GALYIOOTIV(D

‘CL ‘ON AIGVL

‘roqea. Lq patoaood suotyz0d
oy} FO pretk oy} xoF oouvmoTre Suryem Aq poyg-roqeyy roar Lanqpug oy} Jo preré peadesqo Wor, paonped— ‘ALON
283

FITZGERALD ON RAINFALL, ETC.

 

 

 

  

   

 

 

 

 

 

Z99' FIL [869° FES T |TSF Eee en-au 098°L6 |69L°0G |LEF'TG |s4¥°I— [egg-LeT j6re"111—|ezo"e |go0"98 ere'ce—|erF'es |srs'oge 298 ‘et |sco-zet |ro6°sor |**teI0z
986°8E —|SBL"TT9 —_6g0'99 l.ce-sc 9T9°L9 [RATT |LTZ°09 |820°1% |9097€9 jegh'ce fogg'eT |eFo"eF |so6'cz |I9z°6F |eoF'Fs |zzt'TI—|699"0¢ |906°G— |*-- ‘ood
gee-es = |ese"LTe [006 Lt coF'sh |oeL"s— fex6'es |69T-L9 |eIeL |66e°L— |1e8"8T—|eFe'%s |FoT'FI—|¢¢8°L |Fte'es |o0°c9 |toL'ss logt-op |-*+--aoN
TIS" |T86"sFs_—|g09' sar T68'6G |G9F'EL—|Feg"SI—|890°OF [6FG6°OI—jeLz"eF | FO0"SI—/FG9°2— |oTg"9T |e06"Lze—l9Fe"09 |oce’FuT fore-st—l6ez0g [t+ *"390
688°SI— Zee" 9FG— Jaga 1¢ 9FG'18 |ISF-99—|RB89'8G— BBs" F9I—/GET"B—|9L9-9F— |LIG"RL |TTS"Le—|cee"sF—|ZOF Ee—|FLL-LF—|coo G9—|L0L6L |zse-eI—|- + “--adog
BOL'Go— [LoL"ESE— |FIE-RC— Lok T— oIe'L —_ |¥BG"oI—|F¥G"67—|016'E— |oLL"FI—lOTR’Z8— |et9 99—le86°1L—|sFI-es—iscz'%% j908'GF |sLF-zI—lte0'sL—lIz¢°0 [ete SKY
$06 "8E—~ 08G'TI9— j£LT'19—069'L9 _|EREZL—|ees' se—|90F OF—|TSF'86— |z€z"0F—lose' Lo— |zsT'eL—|se0"e9—leLa'L |LF0'eF—|ceees—lT8r'ce—|Lee'sc lesg'Ts—|"-- kane
BaP" FF— LG" TTL— [€L1' 19— TTR 61—|0L8°6S—|60L" TF— |6LL"S9—|Ge0°GL—|289" 98—|SFLF9— |FEg-LO—|FE9 S— |TIT’SL—|L09° 9s—le 16 ec—|899° 99—|s80° 69—|Te6' TT soune
806"TS— [LLF09S— [80% eT OFS'S7—|FeO"GZ |869"E9—|9Rz'S2—|E96'F— |1e0°LT—|¢o9 F— |goz"01 |eTe*9I—loTs-sc—loz6-FL—|Fee"S¢—|8F0°9— |sTe-6z—| LOB GI—|"- «AUNT
080°9 =| L8F 96 BCBS |906°6 | GOT9— |89L70Z |FSE°ST—|Z98 OL |o9L"FG jgsL"6I— Jo6o'os—|Te0"LT—|cLT'% feat of |Fesrsr |4oc°L |ogt-1z |epep  |-+--ady
810'0S —/06G"008 | TaB"FOT |Leg"IT |9L0'SL |cI97Se jf6I'se |erG'OI—iFeF'Ze [ose'T [zeF'9T |9e0"0L |L90°R@ |esL-6o |oFe-1g |os9-ett loss-66 lece-ge |--:-aepT
SEE'Fa (GIF LEB fg99"GF FIGOL |e6L'eF |ecs'F9 |t68'06 |Iz6'sF [96F'G6 |Tz6"sF |9gz'09 |FEF'c9 loze-os |cco'er |gcc-cs |cor-o— |xI6 79 \ceP‘9e |-----qor
Os6's2 — 9GT"S68 /e8z"LZ |OFO'9L |seF so |ggg'eL |ze6'e6 |oLT'S9 |x89°TL |TsT-se |Len'98 |LO6"6L lese-sF |ise'92 |Fet'18 |90z Ge |ozt“sT lezecoz | +--+ uee
“NVaL “IvVLOL
‘O68T | “eS8I ) ‘ss8T | ‘eat | ‘gest | “ssst | ‘Fest | “eget | ‘cssT | ‘ts8t | ‘osst | ‘exet | ‘gust | ‘nest | “oust | ‘oust
“06-9181

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

‘OOVJANS 10YVM B WOT UoTetodvas ATYJUOML poulNss¥ Io pearTesqo YYLM [[eFUTer ATYZWOU pearasqo Jo uostredutoo WOLy—"aLON

‘SHVaA NAGLXIG—‘SNOTIVS) JO SNOITUYL NI DOVEHOS YALIVA JO FUP TUvaAdG 4NQ dO GTaIX GaLVIOOTYD

‘eE ‘ON WIAVE
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IajVM B WO, WOTeIodvas ATYJWOU peuUNsse 10 poartosqo THA [][BFUreL ATqQyUOW paarTesqo fo wostredutod WOT, — ‘ALON

gsro | cee loto't [tert lose't legoo |ese-o |o000— |ts9°0 |rzF0 leto"o fove'o |aot"o— Jocoo josr'r  fecs'o§ fane'0  egv'O |" tvONT
S gost {reso ||oses|rre-t fous foao-z _|eoo'e fosorr ute foou:t _fago'0_ ject: fevr't_ [asy'z jete'y feegro— fogs’ [FOF o—
F  ggo't |yao'9e |lece-0— lease |zt0°F Jogz"o— Jeou't rave |cueo fous-0— |tz6-0— |so9'T_oeLo— |gor'0 |u6a-F foe's |aug'y 088"

680°L |atF'nt |lete'9 |ou6°0 jeer't [e29°0— |9uL"0— leee't |9¥9°0— loots Jesao— [tet-0— |rzeo |ees'r— letg-e J60%'9  |z9n"0-~ [609°T
~ -F6L0— \669°et—|let9't \uoet loet'+ —lete-a— lez¥'T— |tae'e— |e66-c— |zor'e— |oL0°F eTFT— |r8t'2— |eou"T— ]9¥°o— |uoe"e— |910'T_ |069°0—
+P gort— [eco ut—ler¥-1— |o00:0— fose-0 _ |seu-0— Jaxr-t— jeot-o— |ueh-o— jeet'F— love's |esa'e— jeat't— jool't |rsc"e _|ec907 [see's [ato
"2 os't— |e02"oe—lec0'e— Jeue-e _fero-e— |uos-1— |to-2— |¥t6-7— Ja00-e— |eou'e— |ea9's— jovt'e— feoe'o  lertse— |esa'e— teat [Ate 1 jo00
gece |iso-9e—||901-e— Jzzo"1— |sso°e— [tot-z— |cee's— Jon-e— |Ls8'I— lecs"c— |esv'e— [eet '0— |Pu8'e— [cue"1— [eeo:1— |L16 G— |LF0'8~ 819"
F601 Jesr-ut—[ac9°0  Jeor1— loue-t |eute— |eac-T— |u¥z-0— Jose-0— losz-o— |ree'0_|F18:0— |286°0— jeeu-8— Jeou-2— Jee '0— |eoF/T— [oLL 0 —
Z treo loner |looe-o— |tta-0 lete"0— jtzo"t {zos°o— Joag-o |zuz:t jatoT— |ggo"t— |ezg'o— Jett‘0 jogg-T eta" g0F-0 [ToT fFee"0
geez levees |lgeea  \ug'0 zene onae [too t |oraco— let9'% jeag0'0 ses 0 |aer'e |tor'T [fee [ecg-e = fFbL9  OLG'F © 694°T
m@ pose | llscez |tsao levee feears |zzoa eons |g6o'e eons aces feore ats fatr'% | fecu’F | f60°0 Joes’ |LT0°%
et per eee ee jeve ewe imo lees aioe |aoo't |eze> |sece ose'z jutet |eo-e faget jssu'0 aoe"
°

“NVA “was
a ‘ost | ‘oset | ‘east | ‘neat | ‘oset | ‘seer | ‘reet | ‘eset | ‘eset | ‘test | ‘osst | “exet | ‘gust | “LEST | “QUST | “SLT
< “06-2481
3
4 :
8 ‘oovyzans
a
et
cy

‘SUVEX NEALXIG—GNOOEY Aad LAUT O1GAQ NI GOVEUAG AALVA\ FO WIP TUVADY ENO NO CTAIX AALVINOTV)

284

‘FL ON WIV
ETC. 285

FITZGERALD ON RAINFALL,

 

 

 

 

 

 

 

 

 

 

 

 

100's98 $16 "698 Bea" Iss 68F 168 FI6 S68 £86 "SFE £80°9FE ete S9e sees TROL
8zT' FR SOF'SE o9L Ts OOT 98 Ors "es FEISS 190° €8 886' 62
LAL FE 199° L7 SOL" E% £68°SZ SLT "83" FIL FS 9ST" LZ 906° 9%
16°91 BOR LT £98 FL SOT ST 189° LT OLE" LT 220° LT ZEL' 81
G2 0T 190°01 O16 @B8L'8 T86°L S82 THESE 9078
668° IT 98L°OT 0F6 IL 989°6 GL9"6 GLOBE 866° IT 880° FI
TFL 669°9 63 OT 6199 we8"g 9L°9 GFE" L 860° OT
SL6"FL $16'8T EGF RT 189°F1 $60°ST 68L° IL SEL UL COP FT
90% OR £66" 6% LEL GE 688° 969° FE T¥9 FS F630 93 196°S
LOT'6F gse"eg BRE SF zg" LG 096°29 619° FF O9L' LF 189°79
920° TL ZoG "RL ¥08°99 LLF TS LEZ" LB 968°99 118 °69 GFF £9
9¢0°99 FOUTS SIZ"e9 129°69 00% 99 988°79 821 6F 889° Sh sh £apnige 7
188° LE 9LO°FE 798° FE G19" OF 869° 9s €8L°98 BIO @E £69'°SS vreeeee Arena
“@ATISN[IUT *9AISN[ONT “OAISNIOUL “@ATBN[IU]L “@ATSnpOUy “@AISNTIATL “@AISN[OUL “@ATSN[IUT
“O68T 0} SL8T “OG8T 0} SL8T “O68T-SLET ‘0681-8181 “O68I-S18T “068T-B8L8T “O68T-OL8T ‘O681-E98T
- “HINO
OTLSAIA ANY AWE xaogaas “HHVT OLLSATL "HHAIY AWAAaOS “HLVOLIHOOD TAV'T

-adag ‘aLVALIHOOD

 

 

anv HLVOLIOOD

 

 

 

 

 

 

‘HI TAVAY Wad SNOTIVY) JO SNOITTIW NI SCUHQ-UTLVMA ATUHT, JO ATAIX FOVUTAY

‘ST ‘ON ATAVE

 
286 DISCUSSION ON RAINFALL, ETC.

DISCUSSION.

James B. Francis, Past President Am. Soc. C. E.—The recent great
rains and floods in the West and the comparative drought in the East
have led me to consider if this condition can be explained on any
general principles. I suppose the rainfall depends on the evaporation
caused by the heat of the sun, which I take to be uniform, and that
the evaporation and rainfall, taking the earth as a whole, are constant
quantities, although we find practically as to a particular locality very
great inequality. We have had in the West enormous rains and floods;
in the East at the same time the rainfall was extremely small. I
account for it thus: The water evaporated must fall somewhere, but is
irregularly distributed, depending on the currents of air; if there is an
excess in some places there must be a corresponding deficiency in some
other places.

A. Frevey, M. Am. Soc. C. E.—The results shown in the paper just
read have evidently been collected with great care, but it omits one
point which is of importance in the computation of the amount of
storage room necessary in connection with a given water-shed and a
given daily consumption. J refer to the fact that the total amount
drawn from reservoirs in a year of drought, when they are partly or
wholly emptied, is greater than the apparent capacity of the basins,
I have observed several cases where the excess was from 20 to 30 per
cent. and more. In New York, last year, the storage reservoirs were
entirely exhausted and the amount of water drawn from them, exclu-
sive of the natural flow of the streams, exceeded by more than 30 per
cent. the visible capacity.

This result is obviously due to the fact that the ground around the
reservoirs fills up at the same time as their level rises, and that the
amount of water thus stored in the ground gradually returns to the .
reservoir as its surface is lowered. The amount of water stored by
these means necessarily varies with the nature of the ground, being
practically nil for rocky surfaces, and increasing with the porosity of
the materials of which it is formed.

CiueMENS HerscHet, M. Am. Soc. C. E.—The point just made by
Mr. Fieley is one of the two that I wished to make about the paper
under discussion. The Boston observations were, I believe, the first
made on the yield of drainage areas, and, being the first, they have
been worked up with more care and more accuracy than any others
we have. I think, also, that we have had, until recently, only the ob-
servations made on the Boston and the New York water supply drain-
age areas to go from in this country. Now, in the course of time, the
computations and tables that have been made, have gone into more
and more refinements, which is, of course, conducive to an advance of
DISCUSSION ON RAINFALL, ETC. 287

knowledge. But the moment we pretend to work from observations
of this kind and achieve precise results, the more essential it is that
absolutely no modifying causes be left out of the computation. It
thus has come about that this matter of the yield of a reservoir, being
more than its capacity when measured from a topographical map, has
become one of material weight.

The two papers we have recently had on this subject, that of Mr.
Stearns and of Mr. FitzGerald, are notable papers, but embodied in
them is the underlying defect which Mr. Fteley and I have pointed
out.

To illustrate, I will take the paper of Mr. Stearns, who computes
that to yield from a drainage area the moderate quantity of 800 000
gallons per square mile, it is necessary to have something like two
hundred and twenty-five days’ visible supply in store. A storage
capacity of that magnitude is, however, rarely found on any city
water-works in the United States. A result of that sort imme-
diately put me on my guard against the whole series of results
found, and, examining into the matter, I judged that the reason
such results were arrived at was simply that the point had not been
considered, that the water as it rises,-elevates with it the whole water
table of the country surrounding the reservoir. So that the reservoir
volume, as computed from a topographical map, does not represent the
true storage volume; the true storage volume is this computed vol-
ume, together with what may be called the invisible storage, which
latter is under ground. Where, in the one case, we might compute that.
we had got only onehundred and twenty days’ supply, we would have
in reality one hundred and sixty to one hundred and seventy days’
supply in store.

The second point I alluded to is in the way of questioning whether
to accept the results founded solely on the drainage areas of Boston and
New York, as giving results applicable in any and all cases. They are
composed in the main of hills, not of a mountainous character; lie near
the sea-shore, with ample expanse of meadow and farm in the lower
portions. Being accidentally of like character, the impression has
grown up and has been allowed to prevail, that because these two give
concordant results, no others need be expected. They give a yield of
something like 50 or 51 or 49 per cent. of the total rainfall, varying
very largely during the different years, and being even unlike during
years of the same rainfall; for, as we know, the distribution of rainfall
during the year is of the utmost importance. To compute the yield
of any stream from such records, and from the rainfall of the section of
country in which that stream is situated, thus becomes an uncertain
matter. The thing we are all after is knowledge of the flow of a given
stream in cubic feet per second; of what our western friends call ‘‘the
run-off,” and I imagine, that if the measurement of cubic feet per
288 DISCUSSION ON RAINFALL, ETC.

second had been as simple a matter as measuring rainfall, we should now
have a much greater knowledge on the subject than we actually have.
T hope, as time goes on, cubic feet per second will be measured
more and more, and it will follow that inches of rainfall will lose the
importance that is now given them.
To illustrate in figures what I have just stated, I will read some
statistics which I have gathered :

{From the ‘‘ Annales des Ponts et Chaussées. ”’]

January, 1892.

Per Cent.
Durance, above Mirabeau, seven years’ record........ 74
es ‘¢ Avignon, « OE hain 67
Three tributaries of La Loire...........e.eeeeere eens 71
Granit de Morval......... cece cee eccee eee e eee eee 71
Reservoir Gondrexange .... cc cce eee cence ee ceeees 53
Portion of La Seine.......... cece eee ee eee ee eres 53
Reservoir Freyberg 1.0... ccc cece cece cence eee eeees 45

While, as is well known, the general result on the Boston and New
York drainage areas is not quite 50 per cent.

June Ist, 1891, to June Ist, 1892, was a very dry year in the vicinity
of New York. The Croton water-shed yielded in that twelve months
15.74 inches of water; the yield of the Sudbury was, during the same
time, 15.63 inches; the minimum on record on the Croton, 1880, being
15.33 inches.

During the same twelve months, the Pequannock water-shed, above
the intake dam, near Charlottsburgh, situated in the same range of
rainfall and of drought, but consisting largely of mountain slopes,
yielded 23.23 inches of water, being nearly 50 per cent. more than the
rate of yield from the Croton or the Sudbury water-shed.

I will say in this connection that it would be more scientific to
divide rainfall and yields of streams into periods from June Ist to
June Ist, than to divide the year in the usual way, from January 1st to
January Ist, to get true annual yields.

Freperic P. Stearns, M. Am. Soc. C. E.—As a part of my regular
work, I have occasion very frequently to estimate the capacity of pro-
posed sources of water supply. In making such estimates, I have
always found the accurate records of the flow of streams, rainfall and
evaporation, made in connection with the Boston Water Works, and for
the most part under the supervision of Mr. FitzGerald, of the greatest
value. I wish to emphasize one point that has already been brought
out by Mr. FitzGerald, viz., the fact that these records include a most
remarkable period of drought, and that estimates based upon them are
consequently much more conservative than if based upon any other
records with which I am acquainted.
DISCUSSION ON RAINFALL, ETC. 289

I may say in the beginning, that I consider the records of the Sud-
bury River of greater value than those of the other water-sheds of the
Boston Water Works, because there is practically no loss from this water-
shed by the filtration of water through the ground to lower levels, and
there is less complication due to public water supplies upon the water-
shed, diversion of sewage past the lower dam, or by superficial and
underground storage of which no account is taken.

Mr. FitzGerald calls attention in his paper to the fact that the Sud-
bury River records include two years, 1880 and 1883, of most remark-
able drought, drier than any other in this vicinity for the sixty years
from 1830 to 1890. The period of five years from 1879 to 1883, not only
includes these two years, but it also includes three other years, in each
of which the flow was below the average. These facts seem to furnish
ample justification for Mr. FitzGerald’s statement, that “judging by
the past, we may feel assured that we have done all that a reasonable
care demands, if our works are proportioned to the maximum drought
ocurring in so long a period as sixty years.”

By making a comparison between the Sudbury and Croton records,
we are also confirmed in the opinion that the Sudbury records include
a period of most remarkable drought, as will be seen by the following
table :

ComPaRISON oF SUDBURY AND CROTON RECORDS DURING THE DRIEST
PERIODS, VARYING IN LENGTH FROM THREE MONTHS TO SIXTEEN

 

 

 

YEARS. *
Average daily flow for given period
in gallons per square wile.
PERIOD, a

Sudbury. Croton,
BM ONE Sissi vesesca wand see seas Vee ses ema Gee as 95 000 226 000
B MMOMENB sisi cccss aS 5 is iai5 5 (oid saree Sle: Bid yore inane seje terse ss aseneniaiee 181 000 302 400
AN ORL sraress zo ten aimiotaiausieveiarsesg lnlshelg ezasare aleCaie 9 aier=" Hievalbiewes Uupslare 497 000 619 500
DVODES fais sis neies VaNN se Panis s wa aea sins sien wave Aeis Son eieRE 769 000 926 300
TG BY OATS i iaiais ia ajsiste <oscai assis sfasain arsseintain Vigo Sawa. wale gins Becarse 1 079 000 1 057 000

 

 

It will be observed from this table that the average flow from the
Sudbury River water-shed per square mile during the driest periods
of five years or less was very much less than from the Croton, while
the average flow of the whole sixteen years was practically the same.
It is also true that, taking the whole period in each case, the amount
of rainfall was almost exactly the same.

The Croton records would naturally be used in the vicinity of New

 

* The Sudbury records are based upon the sixteen years from 1875 to 1890 inclusive,
The Croton records include the seventeen years from 1870 to 1886, and are taken from a table
made by Mr. A. Fteley, Chief Engineer of the New York Aqueduct Commission, and published
in the Journal of the New England Water Works Association, for March, 1892,
290 DISCUSSION ON RAINFALL, ETC.

York in estimating the capacity of water-sheds; but the above compari-
son at once raises the question as to whether water-sheds in the vicinity
of New York are not about as likely to have these severe droughts in
the future as those in the eastern part of Massachusetts; in other
words, was the great drought on the Sudbury water-shed due to its
location, or was it one of those great variations from the average con-
ditions which occur from time to time in all meteorological phenomena
without being assignable to any known law? Iam inclined to the
latter view, and consequently believe that estimates of the yield of
water sheds in the vicinity of New York, in order to be on the safe
side, should be based upon the Sudbury rather than upon the Croton
records.

The table presented by Mr. FitzGerald, on page 267, is one by which
the yield of water-sheds can be computed with very little labor, and
with as much accuracy as would result from a tedious calculation
based upon the detailed tables appended to his paper.

A table* similar to his, and also based upon the Sudbury records, is
given below. It differs from Mr. FitzGerald’s table, however, in that
his is based upon one square mile of water-shed, including various
percentages of water surface, while mine is based upon a square mile
of land surface with varying areas of water surface in addition.

 

 

Storage required in Gallons per Square Mile of Land Surface to prevent a

 

 

  

Daily volume Deficiency in the Season of Greatest Drought when the Daily Consump-
in gallons tion is as indicated in the First Column, with the following Percentages
per square of Water Surfaces,
mile of land

surface.
0 per cent. | 3 per cent. | 6 per cent. 10 per cent, 25 per cent,
100 ¢00 556 000 3 000 000 8 800 000
150 000 3 400 000 7 109 000 13 400 000
200 000 9 400 000 11 700 000° 18 000 000
240 000 19 000 000 22 200 000 25 400 000
300 000 29 800 000 33 000 000 36 100 000
400 000 52 000 000 64 400 000 57 500 000
5u0 v00 76 500 000 TT 300 000 80 300 000
600 000 102 000 000 10£ 600 000 107 100 000 112 800 000
700 (00 144 400 000 153 000 000 161 600 000 170 700 000 215 900 000
80u 000 202 300 000 210 900 000 219 500 000 228 600 000 273 800 000
900 000 346 200 000 349 200 000 352 200 000 353 900 000 381 600 000
1 000 000 514 600 0U0 516 700 000 619 700 000 528 600 000 532 200 000

 

 

 

 

The second columns of the two tables are directly comparable
because they represent the case where the water surfaces are absent.
It will be seen that there is some difference in the results, though
perhaps not enough to be of practical importance. The other columns
are not directly comparable, but the comparative results can be shown

 

* This table was originally published in the annual report of the Massachusetts State
Board of Health for 1890, page 342, and was also published in the Journal of the Association of
Engineering Societies, October, 1891, and in the Journal of the New England Water Works Asso-
ciation, March, 1892.
DISCUSSION ON RAINFALL, ETC. 291

by the following example, in which it is assumed that the area of the
water-shed, including water surfaces, is 94 square miles, the area of

water surfaces 6 square miles, and the available storage capacity
9 600 000 000 gallons.

By FirzGeraup’s Tasre.
Square miles,

Area of water-shed, including water surfaces. 94
Area of water surfaces............cecaeeeecs 6
Area of land surfaces.......c0c..ceeceeces P 88

Percentage of water surfaces to total water-

shed ........ OFS Matto a yews amen 6.8
Gallons,

Available storage........... Wg eae aa eeme Se 9 600 000 000
Available storage per square mile of water-

SHED 62555: 3 sawed aataawstew amin eseen +«« 102.000 000
Average yield per square mile of water-shed,

from tae e404. pases panes meniee anes 565 000
Daily capacity of whole water-shed......... 53 100 000

By Stearns’ Taswe. ;
Square miles,

Area of water-shed, including water surfaces. 94
Area of water surfaces...............0cecees 6
Area of land surfaces..............0ceeeeees 88
Per cent. of water surfaces to land surfaces.. 6.8
Gallons,

Available storage......... ccc ese cece eens 9 600 000 000
Available storage per square mile of land

BUPTACG I: sion 6:2 cine a'eatavin selging i's Wate Bae 109 000 000
Average yield per square mile of land surface,

from table........... eG Relsetee aide 602 000
Daily capacity of whole water-shed......... 53 000 000

It is sometimes convenient in making preliminary examinations to
remember that ordinary water-sheds where there is no storage, or
where the amount of storage which can be made available is very
limited, as is usually the case with mountain streams, will not furnish
more than 100 000 gallons per day per square mile, while a large pond,
draining a small water-shed, may in some instances furnish as much
as 900 000 gallons per day per square mile of land surface. With the
amount of artificial storage which it is usually feasible to provide upon
water-sheds, the yield is likely to range between 300 000 and 600 000
gallons per day per square mile of land surface.
292 DISCUSSION ON RAINFALL, ETC.

L. J. LeConrz, M. Am. Soc. C. E.—Annual rainfall at and near San
Francisco is subject to great variation, and furthermore, there is great
difference in rainfall, in the same year, between localities only a few
miles apart.

For example, at San Francisco we have as follows:

Inches.
Minim iim fallagscoven 4s:ewe ed widng ss a ee wees = 7.4
Meas iy ah Pa sc erase 4 steeyeee brave veer gare auayeed aedeveys AS: 4 = 49.3
Mean annual sicces:cecsig enti canoes oe tase nee as = 23.0

At the reservoir sites only 25 miles distant, we have:

Manin, £4 5 ice) oevcsela wa teers sectainde we aee tasted ae = 20.0
Wh asxiiin iin fa Lissa <'s srsicvs eraswoate wig ertbetare steimarrerne paalere,t = 81.0
Mean: anniiallcnvsimes <isawes canaguauae da ness 4 = 47.0

Generally speaking, the minimum year’s rainfall equals one-third the
average ; the maximum is more than double the average, and more than
six times the minimum. Two dry years have come in succession,
having only one-half the average rainfall.

The flow of streams is correspondingly irregular. They flow from
December to May, and are dry the rest of the year. During dry years
there is no flow and sometimes no fresh supply enters the reservoirs for
a period of six hundred days. Meanwhile evaporation from water sur-
faces equal 60 inches per year. Hence the practice in California, as to
storage reservoir, is quite different from that in the Eastern States,
where streams are running, more or less, the whole year.

Large reservoirs are a necessity with us and the aim is always to
catch all the flow that the water-shed furnishes, nothing is allowed to
go to waste, asarule. Reservoirs are generally designed on the basis
of 85 million cubic feet of storage capacity for each square mile of
water-shed. This is four to five times as much as most cities have
adopted.

The ‘‘ catch” or amount collected each year is also subject to still
greater variation, but as an average may be estimated at 30 per cent.
of rainfall. During years of light rainfall, even up to 20 inches, the
catch is practically nothing. Where the variation is so great, it is
impossible to make a catchment table which would command con-
fidence, but if we take a wide grasp of the whole subject, I think we
are justified in assuming the following approximations:

 

 

 

RaInFALL, CatcH,
10 inches. 0.5 inches
20 te 2.0 “
30 we 9.0 ee
40 a 18.0 “
50 fe 30.0 ae

 

 
DISCUSSION ON RAINFALL, ETC. 293

Mr. Stearns’ statement that it is impracticable to secure more than
600 000 gallons per day per square mile of water-shed, is a very im-
portant contribution to our list of useful facts. At San Francisco
similar observations have been made, and the final conclusion arrived
at is, that a reliable daily supply of 1.000 000 gallons will require from
4 to 4} square miles of water-shed. This is a result of fourteen years’
experience (1877 to 1891), the mean annual rainfall being about 47
inches. The above catchment table throws ample light upon the true
cause of this difference.

E. Saerman Govutp, M. Am. Soc. C. E.—An important feature of
this paper is its bearing upon the capacity of spill-ways, or overflows
of reservoirs. The author lays down as guiding data, that, in districts
analogous to those treated of, 1 square mile of drainage area furnishes
approximately 1.5 cubic feet per second yearly average, which volume
may be increased a hundredfold, or up to 150 cubic feet per second,
for twenty-four hours, by maximum freshets. This maximum flow is
certainly very large, being 3.4 times greater than that of the Sudbury
water-shed in February, 1886, mentioned by the author. It will be
interesting to make some calculations, to see to what dimensions of
spill-way these data lead us.

Ihave stated elsewhere that, in want of a better, the following
formula gives fairly well the proper average length in feet of spill-ways
in terms of the drainage area expressed in square miles :

L=20/A.

I will use this length in the following calculations, determining
the vertical dimension H, by means of the well-known formula for dis-
charge over weirs :

Q=3.2x Lx VH',
in which Q = cubic feet per second, L = length of weir in feet, and
H = height in feet from sill to surface of smooth water. The co-
efficient 3.2 is, of course, subject to variation ; the above value is a
near enough average for the present purpose.

If, now, we calculated the values of ZL and H by means of these
formulas for a series of reservoirs impounding the flow from water-
sheds respectively of 9, 25, 100 and 400 square miles, yielding 150 cubic
feet per square mile per second, we shall have:

Area, 9 square miles, L= 60, H= 3.63

«25S ee L=100, H= 5,16
« 100 * ee L=200, H= 8.19
« 400‘ ee L= 400, H= 13.00

These values of H represent the height of the cross-section of water
going over the sill of the dam. The crest of the dam must be raised
still higher, the additional height depending upon the nature of the
294 DISCUSSION ON RAINFALL, ETC.

dam, and the probable height of the waves which may be pro-
duced behind it. It is evident that the above figures call for spill-
ways of great capacity. It would be very interesting to know if the
results obtained agree with the practice of our leading hydraulic
engineers.

Some years ago I made calculations for the proper height of spill-
way corresponding to a maximum flow of 40 000 000 gallons per square
mile per twenty-four hours, or about 62 cubic feet per second, this
being, as far as I could ascertain, about the maximum observed at the
Croton dam. I found, using the previously given formula for length,
that the proper height, in feet, was the cubic root of the number of
square miles in the water-shed.

Using this rule for the same areas as those previously taken, we
have:

Area, 9 square miles, L= 60, H= 2.08

ee 20). a L=100, H = 2.92
© 100 *«* « L=200, H= 4.62
«© 400 ** #8 L=400, H= 73.7.

For a maximum discharge of 62 cubic feet per second per square
mile, we should then have the two general formulas for length and
depth of spill-way :

Dey HAC ealosiey es bares esses (2)
in which Z = length in feet; D = total height in feet from sill to
crest ; A — drainage area in square miles, and O=a varying height from
high water-mark to crést of dam depending upon circumstances already
mentioned.

To adapt (2) to a flow of 150 cubic feet per second per square mile,
it will suffice to multiply 7/ A by 1.77. :

Such general formulas cannot be taken as absolute guides, but may
be useful in affording a rational foundation for more special study in
particular cases, the vital question always being: what is the maximum
flow per second which can possibly occur under the most unfavorable
combination of circumstances? Now, any engineering problem con-
sidered in this light, 7. e., that of the most unfavorable conditions
conceivable, naturally leads to a very expensive solution, and it is,
therefore, probable that the tendency will always be in dam build-
ing, to restrict the dimensions of the overflow below what the more
pessimistic view of the case would dictate. In masonry dams built
across rocky ravines, we are comparatively indifferent to the possibility
of the dam being overtopped by a freshet, but in earthen dams this
constitutes, perhaps, the greatest peril with which they are menaced.
It is for this reason, among others, that my opinion remains un-
shaken that such dams should always be provided with a substantial
DISCUSSION ON RAINFALL, ETC. 295

center wall of hydraulic masonry, carried well above the sill or lip of
the dam, and the rip-rapping of the inner slope carried still higher.
As a rule we may expect that the heavier the freshet, the shorter its
duration; so that if a dam thus protected should be overtopped, we
might expect the flood to subside before it should have entirely
stripped the outer slope, and thus caused the center wall to yield,
particularly if liberal discharge culvert capacity is also provided and
made use of. And even if the worst should occur, and the center-
wall be breached, time, that priceless element in such cases, would be
gained, and the catastrophe greatly modified. For the only difference
between the harmless emptying of a reservoir, and a Johnstown
disaster, is one of time.

As our profession, like that of the law, depends in its exercise
largely upon precedent, it is greatly to be desired that statistics
be gathered respecting the dimensions of the overflow of existing
reservoirs, together with their corresponding water-sheds and meteor-
ology.

If the proper depth of spill-way for discharge of 62 cubic feet per
square mile per second be 7/ A, the proper depth for any other quantity,

Q, may be obtained by multiplying 7/ A by the coefficient C, derived
from the relation, @ = V CO, which reduces, using round numbers, to
VQ
16°
We would then have the two general approximate, or rather tenta-
tive, formulas for length and depth of spill-way to discharge a given

number Q of cubic feet per square mile per second, replacing those
before given:

(DU) sradieca es deienate tees L=20 VA ( (as before given.)
arcane es Dom ue x VOL o.

C=

 

MansFieLD Merriman, M. Am. Soc. C. E.—The reason why a rain-
gauge on the top of a building indicates a less amount of rainfall than
one on the surface of the ground, has not yet been made clear. It is
generally assumed that the lower gauge gives the correct result, and
that the indications of higher gauges are unreliable. Mr. FitzGerald
asserts that the signal service observations of rainfall, made on the tops
of high buildings, are untrustworthy. My own view of this matter is
that the higher gauge gives the more reliable result, particularly in
cities. This opinion is not founded on any experimental evidence, and
therefore cannot be regarded as of much value; but as I have not seen
the theory stated by any writer, it may be worth while to note it here
and to give the reasons in favor of it.

The size of a rain-drop, it seems to me, is not constant, but increases
296 DISCUSSION ON RAINFALL, ETC.

as it descends. This is due to the evaporation which constantly goes
on, even during a rain and which is a maximum near the surface of the
ground where the drops of rain are broken up by the impact on trees,
grass and earth. Consequently, the air near the surface of the ground
becomes saturated with moisture, and this is partly taken up by other
drops, whose size accordingly increases as they fall. A rain-gauge on
the surface of the ground hence measures too great a quantity, for a
part of the water which falls into it has fallen before on surrounding
objects.

If there is anything in this theory it would be expected that the dif-
ference in the readings of two gauges, one low and the other high, would
vary with the humidity of the air and also with the force of the wind.
A series of records with several self-registering rain-gauges will enable
a discussion to be made which will throw some light on a question now
in much doubt.

In a large city I can conceive of no better place for a rain-gauge
than on the top of a building. No one would advocate putting it in
an alley or court yard, and a public square filled with trees does not
seem a good place. By locating it on the roof of a building the
influence of heated pavements and walls is largely eliminated, and
these would probably have more effect on the evaporation of water that
has fallen than would be the case in a small town or in the country.
Out on the treeless prairie it seems probable that the height of a rain-
gauge is of less importance than elsewhere.

The only definite reason why a rain-gauge should be located at the
surface of the ground, which I have been able to find, is that at a higher
elevation the drops of rain ‘‘move in parabolic curves ” whenever there
is wind. This reason, however, explains nothing, for, whether the path
of the drops be vertical, or inclined, or curved, if their size remain the
same, the same quantity of water passes through two horizontal planes
of different elevations. As numerous observations show that this is not
the case, I conclude that the size of a rain-drop generally increase as
it descends.

Epmunp B. Weston, M. Am. Soc. C. E.—I have been very much in-
terested in the reading of Mr. FitzGerald’s paper, more especially as
during the past twelve years, at different periods, I have spent con-
siderable time in examining and comparing data relative to the flow
of water from drainage areas. I do not know of any work of this
nature that has been done more carefully than the work upon the
Boston Water Works, and the manner in which the results have been
presented by Mr. FitzGerald seems to be particularly valuable and
instructive.

The following table, giving results from a number of European
water-sheds, which I have compiled from some data that I have at
hand, may be of interest for comparison:
DISCUSSION ON RAINFALL, ETC. 297

TABLE SHOWING THE FLow oF WaTER FROM A NUMBER OF EUROPEAN
WatER-SHEDS.

 

 

 

Average Mean Yea
annual | discharge | Per cent. | Drainage | ;, whlch
RIVERs, ETC. rainfall per int il area In | observa-
in square Tan ne fquare | tions were
inches. mile. Fun On. miles. made.
River Lee, Hertfordshire, 1851
England..c..ssce.seesee ees 98.75 30.5 24 444, tees
os “i ating District
COtlANd 1... .. cee ee gene eee 103.30 362.0 19 11.6 1854
Loch Lubnaig, District
Scotland......cccssescocenes 66.70 225.7 76 69.7 1847
River Bann, and Lough
Neagh, Ireland............. 25.92 94.8 18 2205.0 1856
Brosna, Ferbane, River, 1862
Treland.......... secasececee 35.23 99.0 64 446. { 1856
River Robe, Mayo, Ireland...| 49.85 | 128.9 60 109.4 | {1851
1852 to
River Sadne, France.......... *32.6 86.1 61 11551.0 1855,
inclusive,

 

 

 

 

 

 

* Rainfall average of twelve stations,

I quite agree with Mr. FitzGerald in regard to the unreliability of
some of the earlier records of rainfall. I can recall, among others, a
series of observations covering nearly half a century, that were re-
corded by a man celebrated for his scientific attainments. These re-
cords, that were concluded in 1876 owing to his decease, have many
times been used and quoted as examples of the early rainfalls. The
gauge used for making the observations was located on the top of a
fence about 6 feet above the ground, and the snow recorded as rain-
fall was simply the amount, melted, that was caught in the gauge.
Experiments covering a number of years, that were made under my
direction, show that at this elevation a gauge collects much less rain
than one located about 1 foot above the ground, also that more or less
of the snow that enters a gauge is not unfrequently blown out before
it can be melted and measured. The results that I obtained indicate
that in a gauge located 1 foot above the ground, and the snow
measured at the surface of the ground (by cutting out and melting
a section) the average annual rainfall will measure at least 13
per cent. more than in a gauge located and used as was the one which
I have just mentioned.

B. W. DeCourcy, M. Am. Soc. C. E.—Mr. FitzGerald’s interesting
tables of rainfall induce me to write the following on the rainfall
and phenomena arising therefrom in Washington and Victoria, B. C.
I send some extracts from the records of the different stations kindly
furnished me by the observers in this region. They will be found to
298 DISCUSSION ON RAINFALL, ETC.

vary much in a small distance, only a few miles in position making a
material change.

It is necessary to state that Mr. FitzGerald’s remarks as to the
accuracy of observations will obtain here much more than with the
region he treats of, as many of the observers are volunteers, whom the

oa, a

Ee Ay," : oe “ *

& ° YG aay ae
ie, Yo gl a % "4

sce Rae ;

 Bikynt f a
\ so; sees
NY Wrens a

Fic

PACI

love of science has induced to devote some time from their other pur-
suits to this interesting subject. Still, the rainfall here is very great,
and appears to be influenced by different causes.

Beginning on the foot hills of the Cascade Range of mountains,

 
DISCUSSION ON RAINFALL, ETC. 299

there is a maximum fall, which decreases until those of the Olympic
are reached ; but thence there is an increase until the maximum is
again reached at Neah Bay or the capes, at the entrance to the Straits
of Juan de Fuca, and this maximum prevails along the coast and west
of the Olympic Mountains.

This entire region is covered with a dense growth of timber, con-
sisting of the Douglas fir, spruce, cedar and tsuga-merteusiana (com-
monly called hemlock, though quite a different timber from the
hemlock of Canada and the east); besides, there is a dense growth un-
derneath of sallal, vine maple and small woods, so completely imper-
vious to wind and the solar rays, that there is scarcely any evaporation,
and this, and the fallen timber hold back the rainfall from the streams
and deliver it so gradually, that pronounced freshets are quite uncom-
mon in the large or comparatively large streams.

There are no very large streams in this State west of the Cascade
Range, and where freshets do occur, thay are caused by the melting
snow. However, the entire region is cut up with small creeks, so that
a 40-acre tract will be found watered with numerous small branches.

I have paid some attention to the rainfall in the valley of the Che-
halis (one of our largest streams), which discharges into Gray’s Harbor,
and has a water-shed of about 3 000 square miles. The results show
the smallness of the evaporation. When Chief Engineer of the State
Harbor Line Survey of the different harbors forming the estuary of the
Chehalis, called Gray’s Harbor, I gauged the river and measured it
accurately in several places. :

Aberdeen, Hogmain and Ocosta show a rainfall of 90.82 inches,
which is about that of the entire valley.

The rainfall is 4 689 767 064 934 gallons. At the river’s mouth the
average current is, when running out at low tide, 5 feet per second.

RarnFauu, 1891.

 

 

 

 

    

 

Neap Bay. |Porr ANGELES.| TACOMA, ABERDEEN. seer
January 15.93 2.96 es ns 5.75
February . 6.64 99 2.68 |  ..saee 4.95
March .... 9.80 2.43 2.75 BOE | le | sataveavacs
11.84 2.49 4.91 95285 Sein wns
.91 1.53 1.92 2.75
6.17 94 2.93 4.92
2.60 .00 0.05 1.21
2.11 1.58 2.76 2.02
10.78 2.85 4.17 8.52
10.06 3.33 5.16 6.69
23.06 3.20 7.63 19.96
23.91 5.78 10.55 19.34 oeiatee?
weeeee | wee eee windlass 10.70 For 2 months,
1892.
123.81 27.58 50.88 89.91

 

 

 

 

 

 

 
300 DISCUSSION ON RAINFALL, ETC.

The sectional area is 26 400 square feet. The prevailing winds in
winter are southwesters; in summer, those from the south and south-
west bring rain, and northwest and north or easterly, clear and fine
weather.

Neah Bay, average for eight years........ ....... 104.
Port Angeles, average for eight years............ 28.91
Tacoma, average for five years..............-..+. 42.84

Average annual
rainfall,

Dayton, Washington..........ec cece eee eee e neces 21.75
Fort Canby, Washington............ 0. cece eee eee 45.71
Oly Pladsicwe vaiaseniwes es eee

Tatoosh..... Nis ae raahabestug Bem astlets saasuseaee Gualanudla a stahe aie 75.18
Port Townsend. seus scene pisces cease sewaessoe ven LE00
Portland, Oregon........ cece eee eee nee . 54.64

Monraiy anp ANNUAL RarnFauL, Victoria, B. C.

In Inches. Ten Years—1881 to 1890.

 

 

 

  
  

 

 

 

1881. | 1882. | 1883. | 1884, | 1885. | 1886. | 1887. | 1888. | 1889. |1890. |Mean,

January........... 3.84) 2.28] 5.67) 5.25) 9.15) 3.09) 6.58] 5.02) 2.84] 3.54] 4.72
8.84] 3.55] 3.26] 2.11) 3.84) 3.17) 4.82|° 1.77] 1.12] 2.33] 3.48

1.57| 4.02) 1,56) 0.38) 0.382) 2.94) 5.36) 3.53] 1.50! 1.50} 2.27

2.70} 1.24) 2.02) 1.02) 0.53] 1.67, 0.76] 2.26] 1.83] 0.86] 1.49

1.48} 0.63) 0.74) 0.73] 1.30) 0.45) 1.32) 0.19] 1.01] 0.98] 0.87

a ence waeeee 1.57) 0.42) 0.63) 1.59) 0.25) 1.00! 0.48) 2.23) 0.77| 2.10} 1.09

0.90) 1.24, 0.06) 0,48] 0.06] 0.80) 0.27] 0.34) 0.00) 0.64] 0.48

August...... 0.79| 0.99) 0.00) 1.84; 0.02] 0 73) 0.01] 0.42) 1.04) 0.12! 0.59
September..... 0.82) 0.69) 1.65) 1.66) 4.00) 1.59) 1.16! 1.01) 2.33] 0.33] 1.51
October........ 4.11} 4.30) 1.58) 4.88) 2.73] 2.32) 2.75) 3.35] 2.08] 7 52] 3.56
November..... -| 5.25) 3.32) 6.03} 1.60) 3.47] 1.92] 6.36] 3.69) 1.76) 1.74] 3.4L
December......... 6.13) 5.37) 4.55) 1.95) 2.47) 7.16) 9.18] 1.96] 2.28] 8.28] 4.93
37.99] 27.85) 27.65 23.49] 28.14] 26.84] 38.05] 25.77] 18.56] 29.94] 28.41

 

 

 

 

 

 

 

 

 

 

Tam under obligations for records to Mr. C. P. Culver, attorney at
law, voluntary observer, at Tacoma; Mr. Irvine, at Port Angeles ;
Mr. Charles Addie, at Neah Bay; and Mr. Mack, at Aberdeen. Also to
Mr. A. L. Going, C. E., at Victoria.

I am indebted to R. R. Ball, Captain and Assistant Surgeon U.S. A.,
for the record of rainfall at Port Townsend, Washington, as given
below. Mr. Ball is Surgeon of the Post.
DISCUSSION ON RAINFALL, ETC. 301

 

Monthly average rainfall
and melted snow for
past ten years.

Monthly rainfall at Port Townsend, Washington, from July
1st, 1891, to June 30th, 1892.

 

 

 

 

 

  
  

  

 

1891. Inches, 1892, Inches, Year, Inches,

WAU ssissesilaraardeabrnd arated 38 TODUWALY oe eaace:eis: iene 1.35 1882 2.02
August... 2.62 February. - 1.78 1883 1.68
September . a 1.78 March..... 2a 1.86 1884 1.63
October .....eeseceee 1.12 Aprile scence. vaxenes 2.42 1885 1,38
November..........-+ 3.30 MS Yics esadagrs uasa car 2.90 1886 1.83
December.......... 5.34 PUD, 63,5 deFiaredie da’ 237 1887 1.66
Ls 1888 2.03
1889 1.25

25.12 inches total for year. i aes

 

 

Lewis M. Haver, M. Am. Soc. C. E.—The subject that Mr. Francis
has touched upon is one that is of national importance. I think this
is a question which we should take a little time to consider in conse-
quence of its humanitarian aspects. We want to do as much as we
can to alleviate distress from floods.

I have recently prepared a paper on the subject of the Mississippi
problem for the Engineering Mugazine, expecting to bring the ques-
tion up for discussion at avother time; but as it seems to meto be ger-
mane here, with the consent of the Society, I will give a few abstracts
from it.

“Tn the voluminous discussions and hearings upon this oft-mooted
subject, no one has ever attempted to show that the amount of sedi-
ment ejected from the river’s mouth at all approximates to that received
from the tributaries or eroded from its banks and bed, yet it is a self-
evident proposition that, unless these two quantities be equal, there
must be an annual and permanent deposition in the bed of the stream,
causing that bed, taken in toto, to rise. This opinion has been feel-
ingly denied, and it is even attempted to prove that the beds of the
far-famed Po, Danube, Yellow, Ganges and other alluvial streams of
lesser extent are not rising.

“Tn a state of nature the river has provided its own ‘dump’ by
overflowing the wide valley through which it flows, dropping its
heayiest sediment nearest its edges, and building upa traverse highest
near the brink, sloping away from the borders to the lower swamps
and bayous beyond. Thus the rich alluvial territory from Cairo to the
Gulf has been constructed out of the terrane from the mountains, and
an ample dump has been furnished for the silt-bearing stream; but if
the river be leveed along its entire course, and be compelled to bear its
burden over these thousand miles, it will not be found able to cut
deeper when surcharged with sediment, but it will drop its load_in
every available pool or bend at high water, and assuredly and rapidly
raise its bed. :

«The remedy suggested by a Southern author is to open up the
lateral streams and divert some of the flood waters through more direct,
shorter and steeper channels to the Gulf, the same as has been so fre-
quently urged by Captain Cowden under the name of the ‘outlet’ sys-
tem, and which has been so vigorously opposed by many engineers em-
302: DISCUSSION ON RAINFALL, ETC.

ployed on the river, because of the alleged formation of bars below the
outlets. This feature, however, is even now being carefully studied by
some members of the corps of engineers in charge of sections of the
river, and the data thus far collected would seem to show very grave
doubts upon the supposed injury to the lower reaches from the outlets.

‘« Following Nature’s method, however, and compromising with the
land owner, it would seem practicable to provide a sutlicient number
of large lateral subsiding basins or lakes by enclosing extensive areas
at intervals where thetopography admitted of economical construction,
into which the flood waters could escape, and in which, the velocity
being reduced, a large part of the silt would be precipitated, while,
after the passage of the crest of the flood-wave, the clearer waters from
the reservoirs would return to the river and become useful for naviga-
tion. In short, instead of serving the sole purpose of maintaining the
water supply for low stages, as do the reservoirs in the upper Missis-
sippi, they would also reduce the rate of raising the bed by providing
lateral dumping grounds outside of the bed of the stream, and would
also reduce the flood plane and dangers from inundations. There are
numerous places on the river where, by making return dikes extending
back to the bluffs, many square miles of land, now of little value, might
be utilized for such safety valves for the river, with substantial benefit
and at a comparatively small cost.

‘‘ With reference to'the probable effects of the lateral or outlet plan,
while there is no grand precedent for it, there are many instances which
would point strongly to its success, and one of the best which has re-
cently fallen under my observation is to be found in the lowering of
the flood plane of the Tyne, in England, due to the removal of bars
and obstructions at its mouth and along its lower reaches as far as
Newcastle.

Captain Cowden has reduced his outlet theory to the aphorism
‘make the overflow greater than the inflow and there can be no over-
flow.’ In applying it he proposes to cut off a portion of the inflow by
conducting it through lateral channels to the Gulf and thus preventing
the tributary sediment from ever entering the main stream. This, cer-
tainly, is a desirable feature which appears to have been overlooked.

“Tt does not appear rational to expect any permanent improvement
to a stream until the obstructions at its mouth be reduced and the sur-
face slope in its lower reaches be increased, whether these obstructions
be in the nature of mud or of water fed by tributary courses. The
systematic improvement of the river must treat the problem as a whole,
and provide at high stages for the rapid emptying of its basin at the
outlet, the retardation of its filling by its tributaries, provision ‘for
deposition of its load and temporary escape of its excess of water along
its course; while for the low water stages for navigation the stream
must be canalized so far as practicable to retain a nearly uniform
velocity.”’

B. M. Harrop, M. Am. Soc. C. E.—I want to say a few words, not in
discussion of Mr. FitzGerald’s interesting paper; but in reply to re-
marks relative to the Mississippi River, made part of that discussion
by Professor Haupt. In these remarks, as I understand them, there was
suggestion made of relief from great floods by the diversion of tribu-
taries and by the use for storage reservoirs, of the great basins
which lie on either side of the river.

The further diversion of any of the tributaries presents insuperable
DISCUSSION ON RAINFALL, ETC. 303

diticulties. The Red River is already diverted from the Mississippi,
about 6 miles from its mouth, into and through the Atchafalaya.
The flood discharge of the Red River is about 200 000 cubic fect per
second, while the Atchafalaya has a flood discharge, approximating
twice that quantity. The latter stream therefore serves not only to
divert the Red, but also, in emergency, as an outlet to the Mississippi.
With this exception, the diversion of any one of the tributaries of
the Mississippi River is impracticable.

To divert any other of them would involve a cut hundreds of fect
deep, hundreds of feet wide, and hundreds of miles long, or an under-
taking greater than the construction of the Suez Canal. An examina-
tion of the topography of the valley will establish this.

Regarding the use of the great alluvial basins as reservoirs for sur-
plus flood water, there are difficulties of a different character. The
lands in these basins are owned, under valid titles, by states, corpora-
tions and individuals. Many of them, which would be submerged in a
reservoir, have much value, and are in successful cultivation. It is cer-
tainly true that all these lands are steadily appreciating. The Yazoo
Basin is now substantially reclaimed from overflow, and the value of
the lands therein has, in many cases, if not generally, increased 500
per cent., and homes and occupation have been given to a
steadily increasing industrial population. The owners have in view,
therefore, plans other than this abandonment as overflow reser-
voirs. They propose to complete their reclamation.

But I want more particularly to speak of the engineering objec-
tions to such a project. It is not established that general relief is
found by using these basins as reservoirs to receive and hold back
for a time, the watcr overflowing into them from great floods. An
examination of the gauge record shows that, at the mouths of the
tributaries draining these basins back into the Mississippi, the highest
readings have been reached when a great overflow was returned to the
main trunk, and that while the improvement or completion of a levee
system has, for a first effect, the increase of flood heights along those
parts of the fronts of the basin where overflow had previously
occurred, yet that the transmission of the entire flood between levees
has not had a corresponding effect in the gauge heights at the mouth
of the tributaries. The use of the basins as reservoirs does not, there-
fore, serve as a general relief from excessive flood heights, and it cer-
tainly would not from overflow.

I think that the main idea underlying Professor Haupt’s discus-
sion is that the bed of the Mississippi River is rising. Observations
bearing upon this point have been systematically made for the past,
thirteen years, and a few low water gauge records extend back about
three times that period. It is, of course, impossible that this ques-
tion of an elevation or depression of bed can be settled in so brief a
time; but it is safe to say that, as far as these observations go, they
304 DISCUSSION ON RAINFALL, ETC.

afford no evidence of any general or progressive rise of the bed of the
river. They do indicate that below crevasses or outlets there is a
loss of depth and section, and that the closing of these, by rebuilding
the levees, tends to restore the previous capacity of the bed.

Other facts seem to connect the existing elevation of the bed of
the river with the volume held within the banks. It has always been
observed that the range between high and low water is different in
different parts of the river. It is greatest at or about the mouth of a
tributary when its natural discharge, together with the return of over-
flow into the basin, is added to the volume of the main river. It is less
along the front of the basins, where the discharge is decreased by loss
of volume over the banks. In general figures the flood discharge and
the range from low to high water are both one-fourth greater at the
mouths of the tributaries than they are at intermediate points along
the front of the basin, or 43.5 and 35.3 respectively. In plotting the
low and high water slopes, it is found that the high water line is quite
regular when compared with that of low water, which has depressions
where the flood volume is greatest and elevations where the flood
volume is less. In other words, the irregularity of the low water
line, which generally conforms to the shape of the bed, follows the
depressions of the bed where there is greater, and the elevation of
bed where there is the less flood discharge. This relation of elevation
of bed to flood volume was among the earliest observations. There isno
evidence that it is progressive. On the other hand, there is no evidence
that the maintenance of a more nearly uniform flood discharge through-
out the length of the river by levees has yet caused any greater uni-
formity of bed level, although it is reasonable to expect such a result.

Dersmonp FirzGeraup, M. Am. Soc. C. E.—It is not entirely correct
to say that no account has been taken in my tables of the storage in
the ground, for the reason that more or less of this action has entered
into the measurements of the Sudbury River in the past sixteen
years, due to the drawing down of the reservoirs and Whitehall Pond
during the summers. It was not from lack of some information on
this subject, however, that I decided not to make a separate account
of it inthe tables. The soils surrounding reservoir sites differ so much
in character and the situations of the reservoirs themselves affect this
question to such a degree that it seems to me best, in the lack of ade-
quate data, to leave any such allowance to the judgment of the engineer
rather than to attempt to complicate an already complicated problem
with such a variable and uncertain factor.

The following experiment was made under my direction to determine
- exactly what additional water was received from the storage in the
ground in the case of Basin No. 4 of the Boston Water Works, situated
on the Sudbury water-shed.

This reservoir of 162 acres has. a surveyed water-shed of 6.434
square miles, including the reservoir. Its situation is high rather
DISCUSSION ON RAINFALL, ETC. 305

than low, and the geographical formation is unmodified drift. Its
water comes almost entirely from a feeder at one end of the basin and
so is favorably situated for the experiment. A weir 20 feet wide was
erected at the inlet, with a smaller weir for measuring summer flows,
and a self-recording gauge registered continuously the amount of water
entering the reservoir. The arca of the water-shed above the river was
5.466 square miles, including the reservoir, which left only 0.968 square
mile of contributing water-shed around the margins unmeasured. It
was assumed that this area gave a prorata supply. Rain and evapora-
tion gauges were erected, the latter a floating gauge properly exposed.
It will be impossible in the limits of this discussion to give the details
of the experiment, which covered a period of six months, during which
the reservoir was drawn down 12 feet. The following table, however,
shows the results of the measurements and estimates:

ExprrtmMent to DETERMINE THE YIELD or tHE Water Tapurs Sur-
ROUNDING Basin 4.

 

3 -
Date of Periods, July 1-16. pay 16-Sept. 27.) Sept. 27-Oct. 7.| Oct. 7-Jan. 1.

214.81 to 214.84 | 214,84 to 202.91 | 202.91 to 202.93 | 202.93 to 207.85
15 10 86

 

 

 

 

73

Flow over we g i 9 952 000 52 808 000 2 618 000 190 950 000
Fiow from land below weir 1 2e7 000 7 062 000 366 000 26 515 000
Raintall on water surface, 4 510 000 38 £00 000 516 000 39 825 000
Water irom water tubles,. 6 617 000 66 826 000 QBELODO: | eseinwis sae sax
Drawn through gates,.... 5 960 0UO 704920000 | ....eeeseeee aa va ara ad
Leakage (measured) .... 1 886 OvU 7 696 000 817 000 866 000
Evaporation............. 12 870 00 43 350 000 4 687 0U0 22 365 000
Contributed to water

tubles........ ccc. cee seine Bases Semana teers Sisleaieins ere te 3 099 (00
Storage—gained or lost.. -++1 650 000 —590 4170 000 +860 000 +223 960 000

 

 

From this experiment it was assumed that if the water had been kept
at a uniform level, there would have been a uniform subterranean flow
into the basin of 300 000 gallons per day, derived from rain percolating
through the ground; and with this allowance the water tables con-
tributed to the storage capacity of the reservoir 44900 000 gallons,
while it was falling 12 feet. If these figures are correct, and no expense
was spared to get at the truth, then the storage capacity of the reser-
voir to the 12-foot contour, viz., 590 470 000 gallons, received less than
8 per cent. additional supply from the water tables. It is obvious,
however, that this figure would be very much larger in the case of a
reservoir situated in low gravelly ground ; and, on the other hand, less
in a rock formation.

Admitting that there is a considerable accession to the storage from
the water tables surrounding a rescrvoir, the question now arises, will
it not be better, save perhaps in exceptional cases, to ignore this storage
in order to be on the safe side.

The sixteen years during which the Sudbury has been measured
contained a remarkably dry period, as I have already pointed out; and
in this lies the great value of the results contained in the table and dia-
306 DISCUSSION ON RAINFALL, ETC.

gram for storage capacity ; but is it not presumptuous to suppose that
no greater period of drought will occur in the future? And is it not
better to have the additional help of the water tables against such a con-
tingency, rather than to cut down the capacity of the storage as out-
lined in the paper under discussion? Again, itis always wise to have some
water left in the bottoms of otr storage reservoirs for sanitary reasons.

Mr. Stearns has shown so well the agreement of our figures,
although made on a different basis, that I will not dwell on this point.

Having found from topographical surveys and careful studies of the
Sudbury River Water-Shed, that it will be possible to secure a total
storage of 19 671 000 000 gallons on 75.199 square miles of water-shed,
or 262 000 000 gallons storage per square mile, with 9 per cent. water
surface, and providing in time of greatest drought a daily draft of
785 000 gallons per square mile, with a total daily draft of 59 000 000
gallons from the 75.199 square miles, and at a reasonable cost, Tam led
to believe that it will be found practicakle and wise in some cases to
develop a water-shed to this amount, but I cannot agree with Mr.
Herschel, when he calls this a moderate development of a water-shed.

Professor Merriman will find in the literature on the subject, pub-
lished in England, very full discussions and theories to account for the
fact, which is undisputed in that country among experts, that the
records of elevated gauges are untrustworthy. To satisfy myself in re-
gard to the matter, I once had a series of towers built up to 60 feet in
height, on which were placed rain gauges specially designed for the
purpose of accurate observations, and which have been favorably men-
tioned in the reports of the Signal Bureau. There were nine gauges,
from the surface upwards, placed so as not to interfere with each other,
and daily observations were taken for three years, together with the
velocity of the wind. The results convinced me that there was no
doubt about the inaccuracy of the elevated gauges. The total rainfall
collected at the height of 60 feet was about 82 per cent. of that collected
at the ground level. It does not require these facts, however, to con-
vince us of tie accuracy of the statement made at the bottom of page 254
of my paper. Itis only necessary to compare the observations made on
the tops of high buildings with the observations made in gauges
properly exposed on the ground in the same region, and which agree
very well, even when several miles intervene, to become satisfied on
this point. I believe the Signal Service officers will also endorse my
statements. The wind is probably at the root of the trouble.

Mr. Gould’s discussion in regard to spill-ways is interesting, but I
suggest that, in the majority of situations in which water-works dams
are situated, it is wrong to depend upon the core wail to save an earthen
dam in times of freshet; and, after all, would it not be cheaper, consid-
ered merely as a matter of dollars and cents, to make the spill-way of
ample capacity, rather than to shorten it, and repair the dam whenever
it is overtopped ?
s
°

re