Water consumption in the United States declined 18% between 1980 and 2010.

Water consumption is an issue of concern in areas where water supplies are constrained. Constructing a comprehensive study of how much water is consumed in the United States is a gargantuan task, but the United States Geological Survey does it every five years. It takes several years to put together, and the report Estimated Use of Water in the United States in 2010 came out in 2014. Historical data are also available on the USGS National Water Data Information System data portal.

Data source: USGS Water Use Data for the Nation

Figure 1 shows that water consumption in the USA grew rapidly from 1965 to 1980, but since then has declined. The peak in 1980 was 430 billion gallons consumed per day and by 2010 it had declined 18% to 355. The decline occurred despite the fact that during the period Gross Domestic Product grew by 229% and population grew by 36%.

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Data source: USGS Water Use Data for the Nation

Figure 2 shows similar data, except it is separated into end uses. The shape of the trend matches the one in Figure 1. It is impossible, however, to separate water consumption by end use without either missing some that you should count, or double counting some that you shouldn’t. The result is that, for any given year, if you total the amount used by each end use in Figure 2, it won’t precisely match the amount shown in Figure 1. The disagreement is small, never as much as 5%, and often much smaller than that. It would probably matter if you were doing research, but for our purposes here, it probably doesn’t.

Figure 2 shows that more water is withdrawn for thermoelectric power (nuclear and coal-burning power plants, primarily) than for any other use. Second is irrigation. Both have decreased since 1980. I don’t know the precise reasons why, but if I had to guess, I would say that retiring nuclear and coal-burning power plants in favor of natural gas and renewable energy, improved irrigation practices, and switching to soil cover/crops that require less water were all part of the story.

Public Supply did not peak in 1980, it increased right through to 2005. That makes sense, given that population and GDP have increased. Public supply includes all water delivered by a public water utility.

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Data source: USGS Water Use Data for the Nation

I don’t consider water withdrawn for thermoelectric power to be a true end use. For one reason, it is returned to the environment and used again without much treatment. For another, electricity is not generated for its own use, it is provided to customers for their end uses. Thus, it might be useful to look at water consumption with thermoelectric power excluded. Figure 3 shows the data. Now it becomes clear just how much of our water consumption really goes to irrigation: 60-67% in any given year. And suddenly, public supply looks more significant, accounting for up to 24% of consumption. Industry has made impressive progress in reducing water consumption.

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Data source: USGS Water Use Data for the Nation

Figure 4 shows water consumption by the source of the water: fresh or saline, surface water or groundwater. By far the largest amount is sourced from fresh surface water, and the second largest amount is sourced from fresh groundwater. If dry regions of the country turn to desalination to augment their water supply, look for the saline fraction to grow.

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Data source: USGS Water Use Data for the Nation

One final chart: these stacked column charts are good for showing categorized data over time, but they don’t show the categories for any given year as powerfully as does a pie chart. So Figure 5 is a pie chart showing water consumption in the USA by end use, thermoelectric power included, for 2010. It very powerfully shows that almost half of all water withdrawn in the USA that year went into nuclear and coal-burning power plants. About 1/3 of it went for irrigation.

In the next post I’ll look at water consumption in Missouri. I’m going to take a week off for the holiday, however, so it will appear in January.

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Sources:

Bureau of Economic Analysis. Current Dollar and Real GDP. National Economic Accounts. Downloaded 12/4/2016 from http://www.bea.gov/national/index.htm#gdp.

Maupin, M.A., Kenny, J.F., Hutson, S.S., Lovelace, J.K., Barber, N.L., and Linsey, K.S., 2014, Estimated use of water in the United States in 2010: U.S. Geological Survey Circular 1405, 56 p., http://dx.doi.org/10.3133/cir1405.
U.S. Census Bureau. Part II. Population of the United States and Each State: 1790-1990. Downloaded from http://www.census.gov/population/www/censusdata/Population_PartII.xls.

U.S. Census Bureau. 2011. Table 1. Intercensal Estimates of the Resident Population for the United States, Regions, States, and Puerto Rico: April 1, 2000 to July 1, 2010 (ST-EST00INT-01. Downloaded from http://www.census.gov/popest/data/intercensal/national/nat2010.html.

U.S. Geological Survey. 2014. Water Use Data for the Nation. USGS National Water Information System. Search criteria: Years 1965,1970,1975,1980,1985,1990,1995,2000,2005,2010; Area UNITED STATES; Catogory ALL. Data accessed 12/3/2016 at http://waterdata.usgs.gov/nwis/wu.