A new tool for mapping water use and drought

Dennis O'Brien at the Agricultural Research Service: Farmers and water managers may soon have an online tool to help them assess drought and irrigation impacts on water use and crop development, thanks to the work of two U.S. Department of Agriculture (USDA) scientists.

Agricultural Research Service (ARS) scientists Martha Anderson and Bill Kustas have developed an evapotranspiration (ET) and drought modeling system at the ARS Hydrology and Remote Sensing Laboratory in Beltsville, Md. The modeling system also will help forecasters monitor ET and drought conditions across the United States and overseas.

...The model, known as ALEXI (Atmosphere-Land Exchange Inverse), uses thermal infrared imagery from satellites and calculates soil and plant temperatures that can be used to create maps of ET rates of plants growing in cultivated areas, forests and natural habitats around the world.

ET consists of the water evaporated from soil and plant surfaces, and the water vapor that escapes, or transpires, through plant leaf pores (stomata) as the plants absorb carbon dioxide through photosynthesis. Generally, evaporation cools surfaces, so a cooler land surface is an indicator of higher ET rates and wetter soils.

Water stress elevates soil and leaf temperatures, which can be detected by satellites. Anderson and Kustas can use satellite temperature data to create ET maps. The maps are capable of detecting rivers, lakes, wetlands, riparian buffers, irrigated cropland and areas under water stress...

Physical scientist Martha Anderson and research leader Bill Kustas view a global scale map of evapotranspiration generated with the ALEXI model. Anderson and Kustas are collaborating with U.S. and international researchers from all the major continents in evaluating ALEXI output. Photo by Peggy Greb, found on the ARS website