Spatial-Temporal Variability of Climatic Water Balance in the Brazilian Savannah Region River Basins

The evaluation of water and energy cycles from the estimation of water balance is a fundamental instrument to assess the water potential of a region. Thus, the objective of this study was to evaluate the probable monthly water deficit and surplus in Cerrado river basins and the trend of monthly data on climatic water balance (CWB) and its input variables in the study region. Monthly data on precipitation (P) and reference evapotranspiration (ETo) from January 2003 to December 2019 were used. The deficit and the probable monthly water surplus were obtained from the CWB for each of the 4531 ottobasins. For this, the frequency equal to or greater than 80% of permanence in time was used as a reference. Trend analysis was applied. In the rainy season, most ottobasins showed positive CWB. On the other hand, in the period of lower water availability, most ottobasins showed a negative balance. In all months, there was some ottobasin with a significant trend both for CWB and for P and ETo. In most situations, these trends were a decrease in CWB and monthly P and an increase in monthly ETo.