Rain: A valuable resource |
Care to take a guess at how many gallons of water fall when 1 inch of rain falls on 1 acre of land? |
Rain and snow are key elements in the Earth's water cycle, which is vital to all life on Earth. Rainfall is the main way that the water in the skies comes down to Earth, where it fills our lakes and rivers, recharges the underground aquifers, and provides drinks to plants and animals.
Rain does not fall in the same amounts throughout the world or even in different parts of the United States. Here in Georgia it rains fairly evenly all during the year (especially during weekends, holidays, and picnics), around 40-50 inches per year. But the rain we get in one month might be more than Las Vegas, Nevada gets all year. The world's record for rain belongs to Mt. Waialeale, Hawaii, where it averages about 450 inches per year, and it even received 642 inches during one twelve-month period (that's almost 2 inches every day!). Contrast that to Iquique, Chile, where no rain fell for 14 years (no mosquito problem, at least).
On average, the 48 continental United States receives enough precipitation in one year to cover the land to a depth of 30 inches. That works out to about 1,430 cubic miles of water, which would have a weight (at about 62.4 pounds per cubic foot) or about 6.6 billion tons. The United States is fortunate to be a country where ample rainfall occurs over much of the land area.
Have you ever wondered how much water falls onto your yard during a rainstorm? Using a 1-inch rainstorm as an example, the table below gives example of how much water falls during your storm for various land areas.
Area | Area (square miles) |
Area (square kilometers) |
Amount of water (gallons) |
Amount of water (liters) |
---|---|---|---|---|
1 acre | .000156 | .004 | 27,154 gallons | 102,789 liters |
1 square mile | 1 | 2.6 | 17.38 million gallons | 65.78 million liters |
Washington, DC | 61.4 | 159 | 1.07 billion gallons | 4.04 billion liters |
United States | 3,537,438 | 9,161,922 | 61,474 billion gallons | 232,700 billion liters |
There are 640 acres in a square mile.
Once on the land, rainfall either seeps into the ground or becomes runoff, which flows into rivers and lakes. What happens to the rain after it falls depends on many factors such as:
The table below gives example of how much water (in millions of gallons) falls within the city limits of selected cities when one inch of rainfall occurs.
City | Area (square miles) | Amount of water (million gallons) |
---|---|---|
Atlanta, GA | 131.7 | 2,289 |
Baltimore, MD | 80.8 | 1,404 |
Chicago, IL | 227.1 | 3,947 |
Cincinnati, OH | 78.0 | 1,356 |
Denver, CO | 153.4 | 2,666 |
Detroit, MI | 138.8 | 2,412 |
Honolulu, HI | 85.7 | 1,489 |
Houston, TX | 579.4 | 10,069 |
Jacksonville, FL | 757.7 | 13,168 |
Louisville, KY | 62.1 | 1,079 |
Milwaukee, WI | 96.1 | 1,670 |
New Orleans, LA | 180.6 | 3,139 |
New York, NY | 303.3 | 5,271 |
Philadelphia, PA | 135.1 | 2,348 |
Salt Lake City, UT | 109.1 | 1,906 |
Seattle, WA | 83.9 | 1,458 |
Washington, DC | 61.4 | 1,067 |
City areas are provided by the U.S. Census Bureau, County and City Data Book: 2000, Table C-1 (http://www.census.gov/statab/ccdb/cit1010r.txt). 1 inch of rain falling on 1 acreis equal to about 27,154 gallons of water, and there are 640 acres in a square mile.
Once on the land, rainfall either seeps into the ground or becomes runoff, which flows into rivers and lakes. What happens to the rain after it falls depends on many factors such as:Information on this page is from Rain, A Water Resource (Pamphlet), U.S. Geological Survey, 1988
Can you guess how many baths you can get from a rainstorm?
Visit our Activity Center and find out.
• Rain: A Water Resource, USGS water-information pamphlet
• The water cycle: Precipitation