USGS Washington Water Science Center
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The Issue: Fresh groundwater withdrawals for irrigation from 66 principal aquifers in the United States comprised approximately three-fourths of total groundwater withdrawals in the year 2000. The magnitude of these withdrawals is certainly substantial but difficult to quantify because few states actually monitor groundwater withdrawals for irrigation. Water-resource managers are also interested in how much of a withdrawal is lost to consumptive use (primarily evapotranspiration) and how much ends up as return flow (not used consumptively and thus available for further use.) The magnitude of the consumptive use of groundwater withdrawals for irrigation is, again, substantial but difficult to quantify, and no states monitor consumptive use of the withdrawals.
How USGS will help: By leveraging ongoing groundwater resource assessments in principal aquifers of the U.S., the USGS will develop and demonstrate remote-sensing based methods to consistently estimate consumptive use of irrigation water on national and regional scales.