by Mark Milligan, May 2018
From Utah Water Resources, March 2021:
When it comes to reporting water use, there isn’t a national standard for what is included and what is not, which makes meaningful comparisons difficult. Some cities and states only report certain types of water use and/or apply a credit for water that is returned to the system. Utah includes all potable, secondary and reuse by all users (residential, commercial, institutional, and industrial) in its gallons per capita per day (GPCD). This all-inclusive accounting method means Utah’s numbers look higher than other cities or states that don’t include all water use in their calculations.
Which state uses the most total water? California. In 2010 when considering all sources and uses of water California led the nation in water use with an average of 38 billion gallons per day! Utah’s 4.46 billion gallons per day pales in comparison and ranks us 30th on this list. California may have consumed the most total water, but it had an enormous population of 37.3 million while Utah had only 2.76 million people, which is why it may be preferable to compare per capita use.
Which state uses the most total water per person? Idaho. In 2010 Idaho’s 1.57 million people used 10,955 gallons per capita per day (GPCD) (82 percent was used for irrigation)! Utah used 1,616 GPCD day ranking us 12th on this list. Total water includes categories of commodities that may use water in one state for a product that is consumed or utilized in another state. For example, if Utah water is used to generate electricity sold to California, should the water be legered against the producing state or consuming state? Conversely, California grows many crops that are shipped to Utah, and in this case some of California’s water is shipped to Utah in fruits and vegetables. This may be a reason the USGS does not highlight per capita total use in its report. It does, however, highlight the use of domestic water per capita, water which is locally produced and consumed.
Which state uses the most domestic water per capita? Idaho. In 2015 when considering per capita use of domestic water (both public supply and self-supplied), Idaho topped the nation by using 184 GPCD. Utah was a close second using 178 GPCD. The national average was 82 GPCD. While national domestic water use continues to drop, Idaho and Utah continue to use more. In 2010 the national average was 88 GPCD while Idaho and Utah used a reported 168 and 167 GPCD, respectively.
Which state’s public supply customers use the most water per capita? Utah. In 2010 Utah’s public supply customers used 248 GPCD, ranking us number 1 on this list. Nevada ranked second, using 229 GPCD. How did Utah surpass Idaho which used 210 GPCD and is ranked 5th on this list, behind Wyoming and Hawaii? Although Idahoans’ water use tops the two previous lists, only one percent of the state’s use is categorized as public supply. The very small number of public supply customers apparently do not use as much water as the vast majority of Idahoans who supply their own water through private wells or surface diversions.
WHAT DOES IT ALL MEAN?
An internet search will yield many articles from mainstream, reputable media that have some form of the claim that at 248 GPCD, Utah has the highest per capita water use in the nation. While correct, the claim is only true for public supply customers, a consideration generally not addressed by the media. Interestingly, the 2010 USGS report does not explicitly give any per capita public supply use numbers or rankings, in spite of having the data to do so.
Although state rankings are good for creating attention-grabbing headlines that inspire water-use awareness, they have little to no scientific merit. Arid states typically use more water for landscape and crop irrigation. Farmers usually grow crops that yield higher profit margins and those crops, especially the abundant grass hay and alfalfa hay grown in Utah and Idaho, use a lot of irrigation water. Indeed, irrigation (not including irrigation water delivered from a public supply) accounts for 72 and 82 percent of Utah’s and Idaho’s 2010 water use, respectively.
Utah has historically used copious amounts of water to irrigate valley crops and for landscaping during our dry summer growing seasons. This has largely been possible because adjacent mountains receive ample precipitation. For example, the town of Alta, in the Wasatch Range above Salt Lake Valley, averages over 54 inches of precipitation a year, slightly more than Seattle and Salt Lake City combined. Despite elevated mountain precipitation, many areas in Utah have been supplementing surface water supplies by pumping groundwater at rates that exceed recharge, and some are starting to be impacted. For instance, the need to deepen or replace old shallow wells is a common occurrence in some aquifers. Also, ground-subsidence cracks attributed to land subsidence caused by decreasing groundwater levels have damaged infrastructure and houses in Cedar Valley, Iron County (for more information, see Survey Notes, v. 43, no. 1).
Increasing per capita water use coupled with rapid population growth and projected reductions in both snowpack and streamflow due to changing climate is not sustainable. Nearly 3 million people currently live in Utah and that number is expected to swell to roughly 5.5 million by 2050. To sustain such growth Utah will soon need to make big decisions about conservation measures, water management, and the potential development of costly new supply projects.
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