Which States Use the Most Water? Differences in Water Use Among States
Water consumption, quality, and water supply have become hot button issues in the past few years with hundreds of cities and towns at risk of significant shortages either because available water is not safe to drink or because there simply isn’t enough of it. Recent events, such as drought in California and the Flint water crisis, have focused attention on competing demands for this limited resource.
According to a report from the U.S. Government Accountability Office, two changes will seriously impact the nation’s natural water reserves and soon manifest as water scarcity problems all over the country. One the one hand, climate change and extreme weather events, including droughts and floods, will restrict the nation’s water supply. On the other hand, demands from population growth and energy production look set to increase and will likely complicate freshwater availability and use. As a result, 40 of 50 state water managers expect shortages in some portion of their states under average conditions in the next 10 years.
However, not all regions of the country use water in the same manner. Understanding how states use water and how water needs vary across the country are crucial first steps to making progress in managing the nation’s water. This data visualization presents a breakdown of water usage by state across different categories in 2010. The United States Geological Survey (USGS) collects and published data on national water use every five years for each state. In November 2014, the USGA released water use data for 2010, the latest year available.
Total U.S. water use (i.e., amount of water withdrawn from the ground or diverted from surface-water source) peaked in 1980 at 430 billion gallons per day (bgd), after a phase of steady increase in water withdrawals between 1950 and 1980. By 2010, total water use declined to 355 bgd, lower than it was in 1970. More importantly, though, water use has remained relatively flat between 1985 and 2010 despite continuing population and economic growth and their associated water demands. This can be attributed to adoption of new technologies that enable improvements in efficiency and productivity of water use, new conservation and management approaches, and the changing nature of the economy from water-intensive manufacturing to a less water-intensive service-oriented economy. As a result, per capita water use has also been declining since reaching a peak of 1,941 gallons per capita per day (gpcd) in 1975.
Most of the nation’s water withdrawals go to thermoelectric power generation and irrigation. In 2010, thermoelectric power plants, which are powered by fossil, geothermal, nuclear, and biomass fuels, withdrew 161 bgd, accounting for 45 percent of all withdrawn water. Another 32 percent of withdrawn water (115 bgd) was used for irrigation of farmlands. Finally, public supply—water withdrawn by public and private water suppliers and delivered to users for domestic, commercial, and industrial purposes—represented about 12 percent of total water withdrawals.
However, the national numbers mask significant variation in the level and nature of water use across the country.
There are huge differences in water usage across states with California alone accounting for 11 percent of all withdrawals in the United States in 2010. Withdrawals in Texas accounted for about 7 percent of the national total, followed by Idaho (5 percent), Florida (4 percent), and Illinois (4 percent). Per capita water usage also varies greatly from state to state. Maine used the least at only 338 gallons per person, per day (gal./day). Idaho used the most at 10,955 gal./day.
Variations in water consumption is driven by how water is used across different categories of use. Thermoelectric withdrawals are a large component of the total freshwater withdrawal on a national level. However, the withdrawals are concentrated in specific regions of the country, especially across the Midwest and East, and are smaller in the Western United States. In Figure 3, states are ordered geographically from west to east, in order to show the different geographic distributions for thermoelectric power water use. States in the West like Oregon and Idaho benefit from many hydroelectric facilities throughout their region, which rely on water that is not withdrawn from the source and is thus not classified as a withdrawal by the USGS. Furthermore, coastal states like California, Connecticut, Florida, Maryland, New Jersey, and New York use saline water for most of their thermoelectric power generation, which significantly reduces their dependence on fresh water resources.
By contrast, water withdrawn for irrigation is more widespread across the West, reflecting the drier conditions in the West. A significant portion of total U.S. irrigation withdrawals (83 percent) and irrigated acres (74 percent) were in the 17 coterminous Western States. In Figure 4, the 17 states range from Oregon to Oklahoma (excluding Alaska and Hawaii), with all states ordered geographically from west to east. Surface water was the primary source for irrigation water withdrawal in those states, except in Kansas, Oklahoma, Nebraska, Texas, and South Dakota where more groundwater was used. The magnitude of irrigation withdrawals in Eastern United States is small because of sufficient rainfall.
The amount of water that Americans use for indoor and outdoor uses at residences also tend of vary. An estimated 268 million Americans—representing 86 percent of the U.S. population—relied on public-supply water for their household in 2010. While surface-water sources provided more than half of the total public-supply withdrawal in majority of states, a few states including Hawaii, Florida, Idaho, Mississippi, Nebraska, Iowa, and New Mexico relied on groundwater for 75 percent or more of their public-supply withdrawals. In many of these regions, current demand for water is being met by a diminishing supply of groundwater. If demand continues to stay constant, the reservoir of groundwater will continue to be depleted. Ultimately variation in public supply withdrawal across the United States is a function of population, meaning population trends across the country will be an important aspect of the national water challenge.
The topic of water supplies and variation in regional dependence on water should be front and center in any conversation related to water. The decrease in total water use in the last few years should not be a reason for complacency. Going forward, several factors including climate variability and environmental constraints can intensify America’s water challenges. Addressing those challenges will require innovation and investment in infrastructure and policies at all levels of government.
CSG will be discussing this and other issues impacting the water sector in an upcoming policy academy, "Making Waves With State Water Policies," on December 14 in Las Vegas.