Análise da influência da mata ciliar e da presença de reservatórios sobre a resposta hidrossedimentológica da bacia de contribuição do sistema hídrico Curema - Mãe D’Água

Abstract

The use of models to represent hydrosedimentological processes in river basins has been a useful tool for environmental management. In this research, the Soil and Water Assessment Tool (SWAT) hydrological model was used to predict runoff and sediments under different scenarios of riparian forest preservation and the dynamics of reservoirs. The automatic calibration of flow data for the Piancó station in the period 2004-2011 was performed in SWATCUP, with the SUFI-2 algorithm, and subsequent validation of the model (2000-2003). Four scenarios of riparian forest use were addressed: one, the actual use for the year 2021 (C1), and considering preservation of a strip of 50 meters (C2) and 200 m (C3) throughout the drainage, and C4, which considers the absence of reservoirs upstream. As a result, the calibration and validation obtained NS values above 0.67, and other metrics ranging from “good” to “very good”, with some limitations for representing peak flows. The average sediment production and surface runoff between 1994-2020 were, respectively, 17.96 t/ha/year and 93.16 mm. For the riparian forest scenarios, there was a reduction in surface runoff and sediment production for C2 in relation to C1 of 0.3%, and with an increase in the strip to 200 meters, the reductions increased to 0.8% and 1.65%, respectively, with the application of other techniques in sets being recommended for greater reductions. For the condition without reservoirs, the average monthly flow was 16.45 m³/s, and an increase in sediment production of 4.21%, demonstrating the influence of these dams and numerous other small dams distributed in the basin area. The model demonstrated a better ability to reproduce the trend of real volumes for smaller contribution areas, due to the possible influence of smaller dams upstream of large reservoirs and unrecorded demands that make it difficult to represent more accurately in reservoirs further upstream. The SWAT model proved to be a useful tool for identifying critical areas of sediment production and runoff and for evaluating proposed environmental scenarios.