Integrating Remotely Sensed Estimates of Evapotranspiration Into Long-Term Ground Measurements, Three Gorges Region of China

Accurate estimates of local and regional evapotranspiration are essential for determining water and energy budgets. Data are rare for many under-gauged regions of the world, so the use of remote sensing data to determine these estimates is especially appealing. Remote sensing offers greater spatial coverage (i.e. global) than traditional measures, but has its limitations (e.g., may have less-frequent temporal sampling, and the length of such datasets is limited to the launch of appropriate satellites) and uncertainties associated with the derived evapotranspiration estimates. In this study, we apply the method by Liang and Islam (2001) to estimate the evapotranspiration (ET) for a large area using remote sensing information (e.g., MODIS data). ET estimates from this approach will be compared to the evapotranspiration data measured by two methods (small and large pans) on the ground. Evaluations of the validity of the method by Liang and Islam and other relevant methods for the study region will be provided. The area to be studied is in the Three Gorges Region of China, a region undergoing rapid environmental, land-use, and hydrological change. As the Three Gorges Dam undergoes filling, accurate assessments of the region's hydrology have important implications for its water quality, public health, and economy.