Global Reservoir and Lake Elevation Database
Near-Real Time Monitoring of Lake and Reservoir Surface Elevations
from TOPEX/POSEIDON and Jason-1 Altimetry

The U.S. Department of Agriculture’s Foreign Agricultural Service (USDA-FAS), in cooperation with the National Aeronautic and Space Administration's Goddard Space Flight Center (NASA-GSFC), plans to monitor lake and reservoir height variations for approximately 150 lakes located within major agricultural regions around the world.  This global reservoir height elevation project is unique, being the first of its kind to utilize near-real-time radar altimeter data over inland water bodies in an operational manner.  Initial real-time products from this project have been in operation since December 2003.

The project will utilize near-real time radar altimeter data from the Poseidon-2 instrument on-board the Jason-1 satellite and construct time-series graphs of surface water height variations.  The Jason-1 satellite mission was launched in December, 2001 and replaced data collection from the Poseidon-1 sensor on the Topex satellite on August, 2002. 

Most data processing procedures will closely follow methods developed by the NASA Ocean Altimeter Pathfinder Project, but an intermediate data set with  approximately 4-days delivery time and 15-cm height accuracy will be utilized.    NASA will semi-automate the data processing and deliver updated reservoir elevation graphs every 10 days.  In addition, reservoir height graphs for the past ten years (August 1992- August 2002) will be constructed from Topex/Poseidon data, with 2-3 cm accuracy. 

Satellite radar altimeters can monitor the variation of surface water height for large inland water bodies, similar to the schematic diagram of the Topex/Poseidon measurement system shown below.   However, the technology has limitations such as all potential inland water bodies monitored must be greater than 100 square kilometers, cannot be located within deep valleys, and must lie under the Topex/Poseidon ground tracks.

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