Coupling groundwater and riparian vegetation models to assess effects of reservoir releases

Although riparian areas in the arid southwestern United States are critical fbr maintaining species diversity, their extent and health have been decli ning since Euro-American settlement. The purpose of this study was to devel op a methodology to evaluate the potential for riparian vegetation restorat ion and groundwater recharge. A numerical groundwater flow model was couple d with a conceptual riparian vegetation model to predict hydrologic conditi ons favorable to maintaining riparian vegetation downstream of a reservoir. A Geographic Information System (GIS) was used for this one-way coupling. Constant and seasonally varying releases from the dam were simulated using volumes anticipated to be permitted by a regional water supplier. Simulatio ns indicated that seasonally variable releases would produce surface flow 5 .4-8.5 km below the dam in a previously dry reach. Using depth to groundwat er simulations from the numerical flow model with conceptual models of dept hs to water necessary for maintenance of riparian vegetation, the GIS analy sis predicted a 5- to 6.5-fold increase in the area capable of sustaining r iparian vegetation.