AbstractThe long-term sustainability of irrigated agriculture is contingent on application of cost-effective water conservation measures and improved management in the face of intense competition for limited freshwater resources from municipal, industrial, and environmental/ecological interests. A geographic information system (GIS)–based decision support system (GeoDSS) is presented for maximizing water savings from efficiency improvements and conservation measures through integrated management of large-scale irrigation systems. The GeoDSS incorporates the GeoMODSIM network flow optimization model as implemented within ArcGIS Desktop (ESRI, Inc.) and is applied to the large-scale, complex Imperial Irrigation District (IID) water delivery system in California in support of the IID/San Diego County Water Authority (SDCWA) Water Transfer Agreement. IID GeoDSS automatically constructs a GeoMODSIM flow network within an ESRI geodatabase composed of feature classes for IID canals, drains, reservoirs, farm gate...