Dinâmica do uso e cobertura da terra e sua influência sobre a disponibilidade hídrica: o caso do sistema hídrico Poções-Epitácio Pessoa.

Abstract

Semi-arid regions are characterized by high climatic variability, irregular rainfall regimes, and intense evapotranspiration rates, making water availability one of the main challenges for environmental planning and water resources management. In this context, this study investigated the influence of land use and land cover changes on water availability in watersheds located in the semi-arid region of Paraíba State, Brazil, through the integration of remote sensing and hydrological modeling using the Soil and Water Assessment Tool (SWAT). The model was applied to the Upper Paraíba River basin, the Taperoá River basin, and the sub-basin associated with the Santo Antônio reservoir, and was calibrated and validated using historical streamflow records and statistical performance indicators (R², NSE, RSR, and PBIAS), which were consistent with the criteria recommended in the literature. The simulations revealed contrasting hydrological responses among the analyzed basins. In the Upper Paraíba River basin, an increase in mean streamflows was observed during the rainy season, with an accumulated rise of approximately 9.9% from March to May between 1994 and 2020. In contrast, the Taperoá River basin exhibited a systematic reduction in mean streamflows, with a decrease of about 15% during the rainy season between 1994 and 2047, accompanied by a decline in annual runoff depth from 37.36 mm to 30.59 mm and in sediment yield from 2.06 t ha⁻¹ to 1.70 t ha⁻¹. Micro-scale analysis in the sub-basin of the Santo Antônio reservoir indicated only minor variations in mean streamflows among scenarios, reinforcing the predominance of climatic control over hydrological responses. Overall, the results indicate that although land use and land cover changes exert a moderate influence on annual mean streamflow, their effects become more pronounced in the temporal redistribution of flows, runoff generation, and sediment production. It is concluded that sustainable water resources management in semi-arid basins should prioritize basin-scale planning, the conservation of strategic vegetation cover, and the integrated use of remote sensing and hydrological modeling as decision-support tools.