ESTIMATION OF RIPARIAN WOODLAND EVAPOTRANSPIRATION ALONG THE PLATTE RIVER, NEBRASKA

The U.S. Geological Survey and Nebraska Platte River Cooperative Hydrology Study Group are conducting a study to: (1) measure total evapotranspiration (ET) and estimate rates of ground-water use to satisfy ET consumptive demands (GWET) by riparian woodlands at two representative sites, and (2) calibrate models using the research data to estimate riparian GWET at other locations in the Platte River Basin in Nebraska. The study, based upon data collected from March 2002 to April 2004, will provide better-constrained estimates of GWET in the study area than presently exist and will improve understanding of the impacts of riparian vegetation on water availability.

Study sites were selected based upon analysis of land cover data, woodland surveys, and source-area extent calculations. The investigations at each site will include: (1) determining total ET using eddy-covariance and energy-balance sensors mounted on and around 90-foot tall towers extending 30 feet above the woodland canopy, (2) comparing estimates of GWET determined from ground-water hydrographs with those determined from soil-water and micrometeorological data, and (3) measuring precipitation throughfall to estimate evaporation of intercepted precipitation.