Technical Report of the Project: Climate Change and Human Impacts on the Sustainability of Groundwater Resources: Quantity and Quality Issues, Mitigation and Adaptation Strategies in the Toledo River Basin (Brazil)

A distributed physically-based hydrological model named CATHY (CATchment HYdrology) is used to perform a detailed analysis of the Toledo River basin response to climate projections. CATHY couples a subsurface module, described by a three-dimensional Richards equation, with a surface module, led by a one-dimensional diffusion wave equation. Dynamical coupling is achieved by means of a switching in boundary conditions, from a Dirichlet to a Neumann condition and vice versa. Future climate scenarios are determined from historical time series of daily rainfall and temperature in the study area by applying changes compatible with predictions made by the Intergovernmental Panel on Climate Change (IPCC). A twenty-year simulation is run under four future scenarios and the results are compared with those obtained under an unaltered scenario. It is found that the rise or the lowering of water table level is generally not uniform across the basin, being more significant in the uppermost areas. This suggests that measures of adaptation to climate change effects could be practiced by selecting suitable cultures across drainage basins, especially in the areas where the impact of climate change are most significant.