CoAuthors

Charon Birkett (ESSIC, University of Maryland, College Park, MD, USA); Xu Yang (KBR/NASA-GSFC, Greenbelt, MD, USA); Brian Beckley (KBR/NASA-GSFC, Greenbelt, MD, USA); Curt Reynolds (USDA/FAS, Washington, DC, USA); Elias Deeb (ERDC/USACE, Hanover, NH, USA)

G-REALM is a NASA/USDA funded operational program offering water-level products for lakes and reservoirs that are currently derived from the NASA/CNES TOPEX/Jason series of radar altimeters. The main stakeholder is the USDA/Foreign Agricultural Service, though many other end-users utilize the products for a variety of interdisciplinary science and operational programs. The products are additionally delivered to NASA PO.DAAC archive for the MEaSUREs Earth Science Data Records (ESDR) Program. There is an increasing demand for a more global monitoring service that in particular captures the variations in the smallest (1 to 100 km2) reservoirs and water holdings in arid and semi-arid regions. Here, water resources are critical to both agriculture and regional security. There is also a demand for surface water level products across wetland zones in respect of inland fisheries and assessments of catch potential.
Recent efforts to increase the number of monitored lakes, and to extend the TOPEX/Jason time series to achieve a 25yr observation set for Climate/Earth Record considerations, has shown that great care needs to be taken with respect to the merger of results from multiple instrument platforms, and with respect to the varying location of the satellite overpasses. Effort has also been focused on the creation of products from the Sentinel-3A mission, and on merging the results with the SARAL/ENVISAT/ERS archive. Noting here that all three missions, Jason-3, Sentinel-3A and Sentinel-3B will be utilized for the delivery of operational products for the USDA Decisions Support System.
The use of multiple radar altimeters for operational water level monitoring is also being applied in a parallel program called “Water Watch”. Here, test case river reaches and wetland regions are additionally included for projects looking to natural hazards (flood monitoring) and wetland conservation.