U. S. Department of the Interior, Geological Survey. Rain

Material Information

U. S. Department of the Interior, Geological Survey. Rain
Alternate Title:
U. S. Department of the Interior, Geological Survey. Rain - A Water Resource. 6p. USGS: INF-74-17.
Physical Description:


Subjects / Keywords:
Rain ( jstor )
Water flow ( jstor )
Water depth ( jstor )
Spatial Coverage:
North America -- United States of America -- Florida


General Note:
Box 3, Folder 5A ( WATER SHORTAGE, VOL. I. B3F5 ), Item 1
Digitized by the Legal Technology Institute in the Levin College of Law at the University of Florida.

Record Information

Source Institution:
University of Florida
Holding Location:
Levin College of Law, University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.


This item has the following downloads:

Full Text



1I- I I i

i1II I



I i I I I I I

,illI 11 1
I1" T t



Water is vital to existence on our planet.
Fortunately, it is a renewable resource that
moves in a cycle with neither beginning nor
end. Water vapor, evaporated from oceans,
lakes, forests, fields, animals, and plants, con-
denses and returns to earth as precipitation,
once again replenishing reservoirs, lakes, rivers,
and other sources of water and providing the
moisture required by plants and animals.
The amount of precipitation that falls
around the world may range from less than 0.1
inch per year in some deserts, to more than
900 inches per year in the tropics. One of the
driest spots on earth is lauicue, Chile, where
no rain fell for a period of 14 years. The
world's wettest spot, as shown by data col-
lected from a rainfall gage operated by the
U. S. Geological Survey, is on Mt. Waialeale,
Hawa, where an average of more than 45j
inches of rain falls each year, and where more
than 642 inches fell from July 1947 to July
1948. Although Mt. Waialeale averages slightly
more rain per year, Cherrapunji, India, holds


the sil year record of 905 inches measured
in 1861.
By contrast, the conterminous (48) United
States receives enough precipitation during an
average year to cover the States to a depth of
about 30 inches. This is equivalent to about
1,430 cubic miles of water each year and would
weigh about 6.6 billion tons.
What happens to the water after it reaches
the ground depends upon many factors such
as rate of rainfall, topography, soil condition,
density of vegetation, temperature, and the ex-
tent of urbanization.


For example the direct runoff in a highly
urbanized area is relatively great, not only be-
cause the density of impermeable pavements
and roofs permits less rain to infiltrate the
ground, but also because storm sewer systems
carry more water directly to the streams and
lakes. In a more natural or undeveloped area,
the direct runoff would be considerably less.
In th United States, an average of some
0 percenatf the annual precipitation return_
to the atmosphere by evaporation from land
and water surfaces and bv r
vegetation. The remaining I3 perceg even-
tually reaches a stream, lake, or ea-n rflv
by ovl rd ,noff during and immediately after
a rain, and partly by a much slower route
through the natural ground-water reservoir.
Much of the rain that enters the ground
filters down into subsurface, water-bearing
rocks (aquifers) and eventually reaches lakes,
streams, and rivers where these surface-water
bodies intercept the aquifers. The portion of
the precipitation that reaches the streams pro-
duces an average annual streamflow- in the
United States of approximately 1,200 billion
gallons a day. By comparison, the Nation's

=;3(,, .
.-.-.-.-. .-. ...

"7 .1 .
i :i : : :..

-, ,

-. .

homes, farms, and factories withdraw and use
about 400 billion gallons a day.
The following table lists several major
cities in the United States and the approximate
amount of water each would receive in an
evenly distributed inch of rain.

City Area* Amounts of Water
(acres) (billions of gallons)
Atlanta, Georgia 86,976 2.36
Boston, Massachusetts 29,440 0.80
Chicago, Illinois 141,888 3.85
Denver, Colorado 43,328 1.18
Detroit, Michigan 88,320 2.39
Los Angeles, California 291,264 7.91
Miami, Florida 21,888 0.59
Minneapolis, Minnesota 34,176 0.93
New York, New York 191,808 5.21
Philadelphia, Pennsylvania 82,240 2.23
St. Louis, Missouri 39,168 1.06
San Francisco, California 29,056 0.79
Seattle, Washington 52,352 1.42
Washington, D. C. 43,904 1.19
Areas within corporate limits of cities based upon Bu-
reau of Census 1969 statistics.

Consider for a moment how much rain
water some cities may receive during a year.
For example, Atlanta, Georgia, averages about
45 inches of precipitation per year; multiplying
this by the 2.36 billion gallons shown in the
table as the number of gallons in 1 inch of
rain reveals that some 106 billion gallons of
water fall on Atlanta in an average year. In a
city the size of Atlanta, th per capital water
use I about 110 gallons onr dayor 40,150
gallons per year. Thus, the water from a year's
precipitation, if it could be collected and stored
without evaporation loss, would supply the
needs of about 2,640,000 people or about 4
times the present population of Atlanta.





The following equivalents show the rela-
tionships between the volume' and weight of
water and between the volume and speed of
flowing water.

*One inch of rain falling on one acre of
ground is equal to about 27,154 gallons and
weighs about 113 tons. I
Here is how these amounts are deter-
One inch of rain falling evenly over one
acre (43,560 square feet) of ground amounts
to a total of 3,630 cubic feet or 27,154 gallons
of water (one cubic fo water s 7.48
gallons). A cuic foot of water weighs about
-2,.4 innp,, and a gallon of water weighs
about 8.3 pounds. Therefore, the weight of one
inch of rainfall spread evenly over an acre of
ground is about 226,390 pounds or 113 tons.
*One acre-foot of water (the amount of
water covering one acre to a depth of one foot)
equals 326,000 gallons or 43,560 cubic feet of
water, and weighs 2.7 million pounds.
*One cubic mile of water equals 1.1 tril-
lion gallons, 147.2 billion cubic feet, or 3.38
million acre-feet, and weighs 9.2 trillion pounds
(4.6 billion tons).


RATE OF FLOW (in a stream)

*Water flowing at the steady rate of one
gallon per minute is equivalent to: 1,440 gal-
lons per day; 0.00223 cubic feet per second;
192.7 cubic feet per day; or 0.00442 acre-feet
of water per day.
*Water flowing at the steady rate of one
cubic foot per second is equivalent to 449 gal-
lons per minute; 646,000 gallons per day;
86,400 cubic feet per day; or 1.98 acre-feet of
water per day.
*Water flowing at the steady rate of one
acre-foot per day is equivalent to: 226 gallons
per minute; 326,000 gallons per day; 0.504
cubic feet per second; or 43,560 cubic feet of
water per day.

*Water flowing at the steady rate of one
cubic mile per day is equivalent to: 764.6 mil-
lion gallons per minute; 1.1 trillion gallons per
day; 1.7 million cubic feet per second; 147.2
billion cubic feet per day; or 3.38 million acre-
feet of water per day.

I p.

i L i.::

ii0i71- f-o
*..... Oi ;; BH ,l .

kA 'a u'' I' ar::. A i i '
* .* ..' .... .... : : :. ,i"t. :, ..- ", .. .

. For sale by The Superintendent

Documents, U.S. Government Printing
GPO 1974 0- 550-i'07
Of*'. :

.7 1. W WI :