From Research to Operations: The USDA Global Reservoir and Lake Monitor

Abstract

The Global Reservoir and Lake Monitor (GRLM) records variations in surface water height for approximately 70 lakes and reservoirs worldwide using a combination of satellite radar altimetry data sets. The project was initiated by the U.S. Department of Agriculture’s (USDA) Foreign Agricultural Service (FAS) in cooperation with the National Aeronautic and Space Administration’s (NASA) Goddard Space Flight Center (GSFC) and the University of Maryland (UMD). On-line since the end of 2003, the program focuses on the delivery of near-real-time products within an operational framework and exists within the USDA’s decision support system (DSS) through the larger cooperative USDA/NASA Global Agricultural Monitoring (GLAM) program. Currently, near-real-time products are derived from the NASA/Centre National d’Etudes Spatiales (CNES) Jason-1 mission (post-2002) with archival products derived from the NASA/CNES TOPEX/Poseidon mission (1992–2002) and the US Naval Research Lab’s (NRL) Geosat follow-on (GFO) mission (2000–2008). Validation exercises show that the products vary in accuracy from a few centimeters RMS (root mean square) to several tens of centimeters RMS depending on the target size and surface wave conditions. On a weekly basis, new satellite data are retrieved and products updated. Output is in the form of graphs and text files with web links to other imaging and information resources. The next phase of the program sees an expansion to over 500 lakes and reservoirs via the incorporation of products derived from the European Space Agency (ESA) remote sensing satellites (ERS-1 and ERS-2, 1992–2008) and the ESA environmental satellite ENVISAT (post-2002). Near-real-time products will also be continued via data from the follow-on Jason-2 mission (post-2009). The USDA/FAS utilize the products for irrigation potential considerations and as general indicators of drought and high-water conditions. The monitoring system thus has relevance to water resources management and agriculture efficiency at both the national and international level.