Forecasting streamflow and water availability in a Brazilian semi-arid watershed

Understanding hydrological dynamics in semi-arid regions is challenging due to high climate variability and limited data availability. Studies have been conducted using hydrological modelling as a tool to overcome such limitations. This challenge intensifies when considering future scenarios, particularly the effects of climate change on hydrometeorological variables. In this context, this study aimed to: (i) assess the accuracy of a hydrological model in simulating discharge in a mesoscale watershed located in the Brazilian semi-arid region for different time steps and (ii) evaluate the impact of changes in the reference evapotranspiration (ET0) pattern of the watershed on local water availability. The results showed that the hydrological model can represents the watershed's streamflow very well over an annual time step with Nash-Sutcliffe Efficiency (NSE) = 0.83, Coefficient of Determination (R²) = 0.9 and Root Mean Square Error (RMSE) = 0.16 m3.s-1. It was also found that changes in ET0 have a non-linear effect on the watershed's streamflow, and a 15% increase in the ET0 trend resulted in a 23% reduction in local water availability.