Assessing the impact of climate change on water resources in a semi-arid area in central Mexico using a SWAT model

A Soil and Water Assessment Tool model (SWAT) was developed for the Cuenca Inde-pendencia, a 6992 km(2) watershed with a signif-icant seasonal climate situated in the semi-arid highlands of Guanajuato State in central Mex-ico. This area is dominated by agricultural land cover (43.32 %), followed by pasture (25.7 %). Good to very good results for the coefficient of determination (R-2, 0.66 similar to 0.89) and the Nash-Sutcliffe Efficiency (NSE, 0.65 similar to 0.88) were obtained during both the calibration and the validation periods, while the percent bias (PBIAS) was not so good as the former indicators, but with satisfactory to very good results. According to the projections of seven general circulation models (GCM) under Cou-pled Model Intercomparison Project Phase 5 (CMIP5) for climate change prediction, the Cuenca Independencia may experience more precipitation and higher temperature under emission scenarios of Representative Con-centration Pathway (RCP) 4.5 and RCP 8.5 for the mid-century period (2030 2059), as well as the end of this century (2070 2099), compared to the baseline condition (1970 1999). Potential evapotranspiration (PET) and real evapotranspiration (ET) are predicted to increase continuously. Both mean annual sur-face runoff and aquifer recharge are predicted to increase more rapidly under the condition of scenario RCP 8.5 than RCP 4.5. However, increasing demands of agricultural irrigation are expected to consume the larger water volume seeping into the groundwater system, making aquifer recovery unlikely through natural processes under the current water resources management framework.