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Water Studies Precipitation and Population
The United States Geologic Survey provides the following information:
Rain - a Water resource
"In the United States, an average of some 70 percent of the annual precipitation returns to the atmosphere by evaporation from land and water surfaces and by transpiration from vegetation. The remaining 30 percent eventually reaches a stream, lake, or ocean, partly by overland runoff during and immediately after 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 produces an average annual streamflow in the United States of approximately 1,200 billion gallons a day. By comparison, the Nations's 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*
(acres) |
Amounts of
Water
(billions of gallons) |
Average annual Precipitation
inches |
Population
Est 2007
US Census Bureau |
Gallons of water
per person |
|---|
| Atlanta, Georgia |
86,976 |
2.36 |
|
|
|
| Boston, Massachusetts |
29,440 |
0.80 |
|
|
|
| Chicago, Illinois |
29,440 |
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 Bureau of Census
1969 Statistics.
 Consider for a moment how much rainwater some cities may receive during a year.
"For example, Atlanta, Ga. 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 reveals that some 106 billion gallons of water fall on Atlanta in an average year. In a city the size of Atlanta, the per capita water use is about 110 gallons per day or 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."
Complete the table for each city. Use the most current data you can find.
Evaluate: What does the data tell you?
Is there enough water for each person to use 100 gallons per day?
What factors impact having an adequate water supply?
What changes can be made to deal with a shortage of water?
Annual Climate Review U.S. Summary NOAA | Water Use at Home USGS Q&A | Water Use in the United States
Challenge Question - How many baths can you get from a rainstorm?
Orme Tenn has run out of water
The Math of Sufficient Fresh Water video project
"All of this avoidance of planning has been to avoid having to honestly state that there are limits to the amount of water available
in various parts of the state," said Neill Herring, an environmental lobbyist. "There are concrete limits to growth — and no one wants to admit that."
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