ASTER Observations of the Elephant Butte Reservoir in New Mexico

Between June 2000 and April 2009, the Advanced Spaceborne Thermal Emission and Reflection (ASTER) radiometer aboard NASA's Terra satellite made more than 50 observations of Elephant Butte Reservoir on the Río Grande in central New Mexico, USA. This period includes both high reservoir water levels and drought- induced low water levels.For each observation, we estimated reservoir area using three ASTER Level 2 products from visible and infrared spectral regions, which were expected to provide good land/water contrasts, and three spectral indices or mathematical combinations of ASTER band data: normalized difference vegetation index (NDVI), NDVI- water, and shortwave albedo.Over the observed range of 26-79 km2, we found an approximately linear relationship between estimated reservoir surface area and measured water surface elevation. Given the wide range of viewing conditions encountered, no single parameter or parameter threshold worked best for discriminating between land and water, and supervised classification consistently outperformed automated techniques.