Mapping Evapotranspiration Wins Innovations Award

September 15, 2009
Mapping Evapotranspiration Wins Innovations Award

Innovation Honored by Harvard Kennedy School’s Ash Center for Improving Understanding of Water Usage in Agriculture

Cambridge, Mass. – The Ash Center for Democratic Governance and Innovation at the John F. Kennedy School of Government at Harvard University today announced Idaho’s Mapping Evapotranspiration program as a 2009 Innovations in American Government Award winner. Because over 90 percent of Idaho’s water is used for irrigating agriculture and rainfall amounts remain low, regional water supply disputes continue to grow. In collaboration with the University of Idaho, Idaho’s Department of Water Resources is the first government agency in the nation to develop and use satellite-based evapotranspiration imagery to enhance the understanding of agricultural water usage in the state.

Such data is integral to settling water demand conflicts and offers more accurate and detailed mapping than previous estimates. The program is one of six government initiatives honored at yesterday’s reception in Washington, D.C. which concluded with the premier of 2009 Visionaries, a PBS-produced documentary highlighting this year’s Innovations winners. Mapping Evapotranspiration will receive a grant towards disseminating its innovation around the nation.

Evapotranspiration Defined
Evapotranspiration is defined as the water evaporated from soil and transpired from vegetation. Through the Mapping Evapotranspiration program, Landsat satellites provide visual and thermal images that are processed to determine the state’s irrigated agricultural evapotranspiration. Such data is calculated on a daily, monthly, or seasonal basis and utilizes weather information to provide more precise imagery.

The process is much less expensive and more efficient to calculate than former methods. Individual Landsat images use 30 million pixels to map water usage from areas as large as 10,000 square miles to as small as a single 40-acre field. Previous calculations for quantifying water usage were limited to regional maps with no capability for historical comparison. By tracking usage on a field by field basis, the state can more effectively understand and regulate water use and compare it to past archived usage data.

“Mapping evapotranspiration is important because it shows the amount of water used to irrigate crops – over 90 percent of all water consumed in Idaho. In the past, we mapped where water was being used for irrigation, now we can quantify the total amount used,” said Bill Kramber, senior remote sensing analyst at the Idaho Department of Water Resources. “Using satellite imagery provides greater detail, at lower cost, than previous methods.”

Beyond the Data
The state of Idaho has enjoyed multiple uses for evapotranspiration data beyond what was originally conceived.

  • Wildlife Habitats: Water Resources staff used such data in collaboration with farmers, the U.S. Bureau of Reclamation, and wildlife professionals to implement stream flow restoration projects that ensure salmon and steelhead retain sufficient habitat. The U.S. Fish and Wildlife and the National Marine Fisheries Services currently use such data to determine the amount of water available for endangered species programs.
  • Avoiding Litigation: During times of drought, evapotranspiration data acts as a basis for determining water shortages. In addition, the state’s lawyers have started to use evapotranspiration data to help defend water rights decisions. Residents using water in excess of their rights may be more easily tracked and regulated.
  • Cost Savings: Evapotranspiration data can also be used to more cost-effectively monitor ground water pumped out of aquifers for irrigation wells. While current electricity record calculations cost $119 per well per year, using evapotranspiration data for such monitoring drops the cost to $22.

“Water scarcity is fast becoming one of our nation’s most important resource issues,” said Stephen Goldsmith, director of the Innovations in American Government program at Harvard Kennedy School. “As population and land needs change, mapping evapotranspiration supports more accurate planning and encourages water irrigation conservation. Jurisdictions across the nation can learn from Idaho’s model for solving water-resource conflicts and improving water management.”

For more information, please contact:
Kate Hoagland
Ash Center

Bob McLaughlin
Idaho Department of Water Resources

About the Ash Center for Democratic Governance and Innovation
The Ash Center for Democratic Governance and Innovation advances excellence in governance and strengthens democratic institutions worldwide. Through its research, education, international programs and government innovations awards, the Center fosters creative and effective government problem solving and serves as a catalyst for addressing many of the most pressing needs of the world’s citizens. For more information, visit