As Americans start to fill out the U.S. Census forms they have received in recent days, one government agency is working on another kind of census: a National Water Census to get a handle on the water resources that are available for various uses—irrigation, livestock, public use, thermal electric power generation, aquaculture, mining, industry and well withdrawals.
The water census is part of a broader Interior Department project called the Water Smart Initiative. The initiative tasks department agencies—the Bureau of Reclamation, U.S. Geological Survey (USGS) and office of the assistant secretary for Water and Science—with establishing current water footprints and identifying ways to conserve. The census, overseen by USGS, is an ongoing accounting of the changing quantity, quality and use of water resources across the nation. Congress ordered the project when it passed the Secure Water Act in early 2009 as part of an omnibus public lands bill.
Eric Evenson, National Water Census coordinator at USGS, says his agency’s expertise is determining how much water is available and the consequences of its usage to other users and the environment. That leaves out a whole array of other issues, such as regulatory and economic factors, that also play a role in water availability.
“Many of those go beyond the role or mission of USGS. We are not trying to answer all the questions about water availability, but we can provide the information and tools to allow stakeholders— water resource managers and people who deal with water resources— to answer those questions.” Counting every person in the country is a huge undertaking. Counting every drop of water is even more difficult, but the two are connected.
“Part of counting water includes counting the people who use the water,” Evenson explained. “To determine domestic demand, we rely heavily on population data.” The agency also relies on data from USDA’s Economic Research Service and National Agricultural Statistics Service. The Census of Agriculture, irrigation surveys and the annual Agricultural Resource Management Survey all help gather information that is needed for the National Water Census.
“We work with the Agriculture Department and its agencies to gather information about agriculture’s water use,” Evenson said, “so farmers’ and ranchers’ participation in ARMS and irrigation surveys is automatically helping us do our job.”
Farmers and ranchers will benefit from the water census, Evenson says, because the information it gathers will give state water authorities and others the tools they need to develop water plans. “It’s important to understand accurately the trends that have been occurring in the past and use them to chart the future,” he explained.
One of the changes he says has occurred in agriculture is that the number of irrigated acres in the West has declined and leveled off over the last 15 to 20 years. Meanwhile, irrigated acreage in the East has been growing since the 1950s. “We believe that is associated with changes in crop patterns,” Evenson said, “and the desire to ensure that you’re going to get a yield off of that cropland during a drought.” The South has suffered from severe droughts in recent years.
Another change is a continual decrease in the amount of water needed to produce the same if not more crop yields. Everything from better irrigation technology, more usage of drip irrigation and downward nozzles on central pivot systems, to highyielding hybrid and biotech seeds has lessened for many crops the amount of water used per yield. “It’s important to acknowledge that,” Evenson said.
Still, agricultural irrigation is the second-largest use of water in the U.S., making up 31 percent of withdrawals. Thermal electric generation is the No. 1 use, accounting for 80 percent of withdrawals. However, with thermal electric, more of the water is returned to the environment after it is used to make steam or as a coolant. Irrigation, while making up a smaller share of water withdrawals, is what’s called a more consumptive use—less of the water goes back into streams, rivers and other water bodies.
However, irrigation is undoubtedly important. It takes water to grow food, so we all can eat. As obvious as that is, it hasn’t made water conflicts any easier to navigate. One thing the 2010 Census is likely to show is continued population growth in most cities and towns. As population rises, so does competition for water. In order to prepare for and address future water conflicts, Evenson says, you first have to know what the uses are, how much water is needed, how much water is available and its quality and the cost of removing substances that would limit a certain use.
“Being able to characterize needs for water and how much flow is available is part of trying to ensure enough water is available for everybody’s needs,” he said.