Climate Change and Decision Making in the San Pedro Basin Aquifer: From Global Climate Models to the Decision Support System

The current work presents the coupling of climate model projections and the groundwater budget of the San Pedro Basin for a Decision Support System Model (DSS), building on the contributions of Serrat-Capdevila et al. (2007) and addressing some of its limitations. After a reliability ensemble analysis and a bias correction to select and used the best climate models for the region, precipitation estimates at the basin scale were used to calculate recharge using a basin-wide lumped equation, whose results were then disaggregated temporally and spatially into seasonal recharge values. As recharge types and rates vary with precipitation regimes along the year, a seasonal approach is essential to quantify hydrologic impacts from seasonal rainfall changes. Temperature projections were used to infer changes in recharge due to evaporative losses and increases in the riparian corridor’s evapotranspiration. Estimating future changes in riparian ET was possible with existing data in the basin, allowing for analysis of temperature controls on ET and the growing season. Using different approaches such as Hargreaves reference crop equation, and the concept of surface resistance in Penman-Monteith equation, combined with GCM meteorological projections, it was possible to issue future projections of ET in warmer scenarios. At present, the previous changes in recharge, temperature and riparian ET, are being linked to the Decision Support System Model developed in the San Pedro Basin. A fast to run set of response functions have been used to supply the DSS model with the results of a finite-difference groundwater model, allowing for the inclusion of numerous climate change scenarios into the Decision Support System of the basin. The ultimate goal of the current work is to help set a new sustainable yield accounting for climate change impacts and beyond congressional bill 321 and its current associated goals to be attained by 2011 in the Basin.