Crop Explorer is a program of the U.S. Department of Agriculture's Foreign Agricultural Service (USDA-FAS) in co-operation with the National Aeronautics and Space Administration, and the University of Maryland. USDA-FAS is routinely monitoring lake and reservoir height variations for many large lakes around the world. The program currently utilizes near-real time NASA, CNES and NRL radar altimeter data over inland water bodies in an operational manner. The surface elevation products are produced via a semi-automated process and placed at this web site for USDA and public viewing. Monitoring height variations will greatly assist the USDA/FAS Office of Global Analysis to quickly locate regional droughts, as well as improve crop production estimates for irrigated regions located downstream from lakes and reservoirs. All targeted lakes and reservoirs are located within major agricultural regions. Currently ~75 lakes are included but his will expand to ~600 as the program incorporates data from the ESA ERS and ENVISAT missions. Reservoir and Lake height variations may be viewed in graphical and text format by placing the cursor on and clicking the continent and lake of interest.