A preliminary synthesis of major scientific results during the SALSA program

The objective of this paper is to provide an overview of the primary result s of the Semi-Arid Land-Surface-Atmosphere (SALSA) Program in the context o f improvements to our overall understanding of hydrologic, ecologic, and at mospheric processes and their interactions in a semi-arid basin. The major findings and future research needs associated with the different core compo nents of the program are emphasized. First, remote-sensing investigations a re discussed, especially those directed toward taking full advantage of the capabilities of the new generation of satellites (ERS2/ATSR2, VEGETATION, LANDSAT7, NASA-EOS). Second, we discuss parameterization of the water and e nergy fluxes in arid and semi-arid regions, with special emphasis on method s to aggregate these fluxes from patch scale to grid scale. Third, we addre ss the issues related to grassland ecology and competition for water betwee n native grass and invasive mesquite species. Fourth, findings related to t he interactions between surface water, ground water, and vegetation in a se mi-arid riparian system are discussed. Next, an assessment of land use and land cover change over the entire basin over a quarter century is reviewed. Finally, unsolved issues and the needs for further research are outlined. (C) 2000 Elsevier Science B.V. All rights reserved.