Water Science for Schools
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Trends in Water Use in the United States, 1950 to 2005How has America's water use changed over the last 55 years? Are we using more or less water, and are there trends for different kinds of water use? There is a lot of information in the bar graph below. It shows the amount of water used for various categories of water use from 1950 to 2005. This chart shows the trends in surface-water, groundwater, and total-water withdrawals for the Nation from 1950 to 2005. Notice how the relative amounts of surface- and groundwater withdrawals (in percentages) has remained fairly constant. About three-fourths of the water used in America comes from surface water. What is remarkable about this chart is that it shows that the Nation's water use peaked in 1980 and has been fairly steady since then. Many of the stresses for greater water use have risen since 1980, such as population, the need to grow more food (irrigation), more industry,etc, yet total water use has not risen. This shows that water conservation efforts and greater efficiencies in using water have had a positive effect in the last 30 years. 
Trends in total water withdrawals by category, 1950-2005The bars that stand out most are the yellow ones -- water for electricity production. Electricity water use increased almost 500 percent from 1950 to 2005. (All 2005 water use information is from the report Estimated use of water in the United States in 2005.) Irrigation water use increased by about 43 percent—it takes more water to grow food for our increasing population. Notice how after 1980 water use started to decrease a bit, possibly due to the Nation making more use of water-conservation measures. The purple public-supply boxes are important. Notice how they continue on an uptrend. Public-supply water (water withdrawn by the local county and city water departments and delivered to homes and businesses) goes to serve the Nation's normal water uses, such as supplying industries, restaurants, and homes with water. The Nation's ever-increasing population demands ever-increasing supplies of water. 
Trends in population and fresh surface-water use, 1950-2000The majority, about 77 percent, of freshwater used in the United States came from surface water in 2005. The largest user of surface water is the thermoelectric-power industry, which uses it to cool electricity-generating equipment. Most of this water is returned directly to the environment, unlike in irrigation, in which much of the water is consumed (evaporated, transpired by plants). Only the public-supply sector, which used about 13 percent of fresh surface-water withdrawals, has increased continually since 1950. This makes sense since publicly-supplied water goes directly towards America's ever-growing population. Since 1950, the groundwater portion of total water withdrawals in the United States has remained at about 80 percent.. 
Trends in population and fresh groundwater use, 1950-2005Groundwater is vitally important in supplying water for our Nation's everyday water needs, with the most significant use being for irrigation and public water supply. Since 1950, the groundwater portion of total water withdrawals in the United States has remained at about 20 percent. The vast amount of groundwater used is freshwater, with a small amount of saline water going to mining uses. Groundwater is used to irrigate crops and supply homes, businesses, and industries with water. 
Trends in freshwater and saline-water withdrawals, 1950-2000
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