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Scientists develop tool to map water use and drought

US: Agricultural Research Service (ARS) scientists Martha Anderson and Bill Kustas in the US developed an evapotranspiration (ET) and drought modelling system at the ARS Hydrology and Remote Sensing Laboratory in Beltsville. The modelling system aims to help forecasters monitor ET and drought conditions across the US 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 vapour 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 used 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.
The work is funded by the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA). NOAA plans to use the system to generate ET estimates over the continental US. The system is expected to become particularly relevant as climate change presents challenges for growers and water managers in areas such as the Texas Panhandle, the Florida Everglades and the southwestern US.
Source: USDA