Projected climate change impacts on groundwater recharge in the Urucuia aquifer system, Brazil

In this work we analyse the effects of climate change on the recharge and the groundwater flow of the Urucuia Aquifer System in western Bahia State, Brazil (UAS-BA) in the period 2041-2060. We assessed possible changes and impacts on groundwater recharge with four climate models from the sixth phase of the Coupled Model Intercomparison Project Phase 6 (CMIP6): ACCESS-ESM1-5, CanESM5, EC-Earth3 and MIROC6, under scenarios SSP1-2.6 and SSP5-8.5 (Shared Socioeconomic Pathways-SSP). Visual Balan 2.0 aquifer recharge assessment code, and the MODFLOW hydrogeological model were used to analyse the impact of future climate changes on the recharge. The projections of relative change in precipitation, under the SSP1-2.6 scenario, show a precipitation reduction between 5% and 20%, using ACCESS-ESM1-5, CanESM5 and EC-Earth3 models. Using SSP5-8.5 scenario, these models behave differently, while the CanESM5 and EC-Earth3 models indicate an even greater decrease in precipitation, with values up to 35%, the ACCESS-ESM1-5 projects an increase in precipitation of up to 25%. Using MIROC6, though, an increase of up to 10% in precipitation in the UAS-BA is expected, under both scenarios. Regarding temperature, all the models agree with a warming in the future varying from 2 to 3 degrees C. Recharge projections calculated using the Visual Balan 2.0 indicated in general a reduction between 8% and 43%. Using the MODFLOW model, the results show a reduction of recharge to the aquifer varying from 3% to 45% using CanESM5, EC-Earth3 and MIROC6. The ACCESS-ESM1-5 has a 26% reduction (5% increase) under SSP1-2.6 (SSP5-8.5). Furthermore, projections indicate a downward trend in the water table in the northern portion of UAS-BA, reaching a maximum drop of up to 12 m with the CanESM5, under SSP5-8.5 scenario.