Impacto das mudanças da cobertura e uso da terra nos processos hidrológicos da bacia do Rio Pojuca, Bahia, Brasil.

Abstract

By producing large-scale transformations in the river basins they occupy, societies have a decisive impact on the hydrological processes, causing changes in the quality and quantity of water available to satisfy multiple demands. This work aims to analyze the influence of land use and land cover change on the production of water and sediments in the Pojuca River Basin, in the state of Bahia. As a case study, the Pojuca river basin (in Bahia, Brazil) was modeled. The evolution of land cover and land use in this basin was evaluated in the period between 1985 and 2020. Four land cover and land use scenarios were constructed (APP recovery, Total deforestation, Total reforestation and Trend – 2055). The model was calibrated using two different methods: (i) Single Site Calibration – SSC and (ii) Simultaneous Multi-site Calibration – SMSC. Most of the statistical performance indicators attested to the ability of the model calibrated with both methods to adequately simulate the flows and sediments in the basin's outflow. A tendency to overestimate results during the validation period was observed. In relation to the flow results at the internal point of the basin (upstream fluviometric station), the model calibrated with the SMSC method simulated flows closer to the observed flows, presenting superior performance to the SSC method. The simulation of the different scenarios indicated that the total reforestation of the basin resulted in an increase in average flows (15%), minimum flows (11%), base flow (18%) and recharge to the deep aquifer (17%). The trend scenario for 2055 indicated a 25% increase in surface runoff. In general, the behavior of the basin in terms of flow and sediment production proved to be little variable between the scenarios.