A GIS-based Management Tool to Quantify Riparian Vegetation Groundwater Use

Rapid population growth in semiarid regions of the southwestern United States is increasing the demand for water. In many cases, groundwater is mined from valley aquifers to meet this demand, which results in declining water levels in the aquifers. Riparian corridors are vulnerable to these declines since near-surface groundwater supports baseflow in the rivers and the abundant vegetation/habitat found therein. This is the case for the San Pedro River Basin in southeastern Arizona and northern Mexico. In such basins, effective management of water resources requires accurate measurements of water fluxes, including the evapotranspiration from the vegetation in the riparian corridor. This paper describes a management tool to help estimate groundwater demand from riparian vegetation along the San Pedro. The tool combines calibrated, process-based ecosystem models of riparian water use with a vegetation map to provide watershed-scale estimates of riparian vegetation groundwater use. This model is GIS-based to provide a user-friendly application that allows the user to change the vegetation cover in order to evaluate the effects of vegetation change (e.g., prescribed or accidental burns, rehabilitation of abandoned agricultural fields, shrub removal, etc.) on the groundwater demand