Water use across US has been decreasing since 2005, has now reached pre 1970 levels, says the U.S. Geological Survey (USGS) study[i] published on June 19, 2018. According to a new USGS report[ii], 445 BCM (Billion Cubic Meters, all BCM figures are annual figures) of water were withdrawn for use in the United States during 2015. This represents a 9 percent reduction of water use from 2010 when about 489 BCM were withdrawn and the lowest level since before 1970 (511 BCM).
California biggest user In 2015, more than 50 percent of the total withdrawals in the United States were accounted for by 12 states (in order of withdrawal amounts): California (9% of total water withdrawal), Texas (7%), Idaho, Florida, Arkansas, New York, Illinois, Colorado, North Carolina, Michigan, Montana, and Nebraska. Florida had the largest share of saline withdrawals, accounting for 23 percent of the total in the country, mostly saline surface-water withdrawals for thermoelectric power generation. Texas and California accounted for 59 percent of the total saline groundwater withdrawals in the United States, mostly for mining.
Category wise consumption For the first time since 1995, the USGS estimated consumptive use[iii] for two categories in 2015. The consumptive use was 5.96 BCM, or 3 percent of total water use for thermoelectric power generation. Consumptive use was 101.14 BCM, or 62 percent of total water use for irrigation.
Water withdrawn for thermoelectric power generation was the largest use nationally at 183.77 BCM, with the other leading uses being irrigation and public supply, respectively. Collectively, these three uses represented 90 percent of total withdrawals. Water withdrawal for Thermoelectric power decreased 18 percent from 2010, the largest percent decline of all categories. Irrigation withdrawals (all freshwater) increased 2 percent, mining withdrawals increased by 1% and withdrawals for livestock saw no change. Public-supply withdrawals decreased 7 percent.
A number of factors can be attributed to the 18 percent decline in thermoelectric-power withdrawals, including a shift to power plants that use more efficient cooling-system technologies, declines in withdrawals to protect aquatic life, and power plant closures. This reduction of 39.8 BCM accounts for 89% of total reduction in withdrawals.
Thermoelectric Power accounted for 41% of all withdrawals, surface water supplied almost all withdrawals; 72 percent of the surface water withdrawals were freshwater.
Irrigation Withdrawals for irrigation were 37 percent (163 BCM) of total withdrawals, and 42 percent of freshwater withdrawals. Lands irrigated with sprinkler or micro-irrigation systems accounted for 63 percent of total irrigated lands. Surface water supplied about 52 percent of the total irrigation withdrawals. The 17 conterminous Western States accounted for 81 percent of total irrigation withdrawals, and 74 percent of the total irrigated lands in the United States. The trend[iv] toward using more efficient irrigation systems continued with 10 percent more irrigated lands using sprinkler systems (including micro-irrigation) in 2015 than in 2010; lands using surface (flood) irrigation systems decreased by 11 percent.
Livestock, Aquaculture Withdrawals for livestock and aquaculture combined were 3 percent of the total withdrawals in 2015. Total withdrawals for livestock were 2.76 BCM and 62 percent was from groundwater. Total withdrawals for aquaculture were 10.43 BCM and 79 percent were from surface water.
Self supplied industries Self-supplied industrial withdrawals were almost 5 percent (20.45 BCM) of total withdrawals, and surface water provided 82 percent. Withdrawals for mining were about 1 percent (5.53 BCM) of total withdrawals, and groundwater supplied 72 percent, mostly (65 percent) from saline water.
Public supply As during 2005-2010, withdrawals for public supply declined during 2010-2015, despite a 4 percent increase in the nation’s total population (325 million in 2015). The number of people served by public-supply systems continued to increase and the public-supply domestic use declined to 311 lpcd (liters per capita per day) in 2015 from 333.5 lpcd in 2010. Total domestic use (public supply and self-supplied combined) decreased from 330 lpcd in 2010 to 311 lpcd in 2015. 61% of public supply withdrawals were from surface water.
Public-supply systems deliver water to domestic, industrial, commercial, and other users, and 60 percent of public-supply withdrawals provided 87 percent of the United States population (283 million) for domestic indoor and outdoor residential uses. Other residences are self-supplied from wells or other sources; these withdrawals were about 1 percent (4.50 BCM) of total withdrawals and provided water to about 13 percent (42.5 million) of the United States population. Groundwater was used for 98 percent of the self-supplied domestic withdrawals. Clearly, the domestic water use levels are very high in USA.
Water Sources It is interesting to know that USA also keeps account of saline water withdrawals both from surface and groundwater[v].
- Fresh surface-water withdrawals (273.6 BCM) were 14 percent less than in 2010
- fresh groundwater withdrawals (113.7 BCM) were about 8 percent more than in 2010.
- Saline surface-water withdrawals (53.3 BCM) were 14 percent less than in 2010
- saline groundwater withdrawals (3.23 BCM) were 5 percent more than in 2010.
Every 5 years since 1950, USGS has compiled and estimated water-use information, to evaluate water-use trends through time. Total withdrawals steadily increased from 1950 (248.7 BCM) to the peak in 1980 (594 BCM), declined in 1985 (548.5 BCM), and then remained fairly steady until 2005 (566.5 BCM).
In Conclusion It is great to see USGS putting this state wise, water source wise, water use wise, year wise information in public domain promptly every five years. One wishes India were to progress in that direction. We will first need an institution that is capable of doing this independently, transparently and consistently, without having any conflict of interest. The chief water information gatherer of India today, Central Water Commission does not quality on any of these counts. Most importantly, CWC wont be able to do this task independently as long it is also responsible as developer, regulator and policy maker, among other tasks.
This amazing information source, however, does not say what are the water withdrawals for environmental uses, or evaporation losses from reservoirs or water use in forests in USA. There area also non consumptive water uses, for example for fisheries or navigation, which are also not mentioned here. Possibly some of these figures may be available in other reports.
[iii] Consumptive use is the fraction of total water withdrawals that is unavailable for immediate use because it is evaporated, transpired by plants, or incorporated into a product.