Hydrosedimentological modeling in a headwater basin in Southeast Brazil

Abstract

Hydrosedimentological modeling is a useful tool to predict the water dynamic in a basin and for water resources management. This study aimed to i) evaluate the ability of Soil and Water Assessment Tool (SWAT) to model sediment load and continuous monthly streamflow in the Mortes River Basin (MRB) in Southeastern Brazil; ii) estimate the sediment yield spatially distributed by sub-basins; iii) estimate the sediment load export to the Funil Hydroelectric Power Plant reservoir (FHPP), located in the MRB outlet. For the sensitivity analysis, calibration, and uncertainty analysis of the model, a semi-automatic calibration in SWAT-CUP version 5.1.6 software with the "Sequential Uncertainty Fitting" algorithm was used. To evaluate the ability of SWAT to reproduce the continuous MRB monthly streamflow and sediment load, statistical indexes, and graphical analyses were used to compare the simulated and observed data. For the sediment evaluation, a spatial and temporal comparison of sediment yield maps was used as well as the sediment yield observed in sub-basins, aiming to identify the areas with a more significant contribution to the sediment generation in the basin. The results demonstrated that SWAT performed satisfactorily in simulating both monthly sediment load and streamflow. For discharge calibration, 99 % of the measured data were bracketed by the 95 % prediction uncertainty (95PPU), and for validation, 97 % of the data were bracketed by the 95PPU, which indicates proper bracketing of the measured data within model prediction uncertainty. Uncertainty analysis indicated that 95PPU could capture 78 % of the sediment loads measured during the calibration and 72 % of the measured data during the validation period at MRB. The hydrologic response unit with pasture and Argissolos (Ultisols), Neossolos Litólicos (Entisols), and Cambissolos (Inceptisols) combined with undulated relief were the main areas responsible for the highest sediment contributions. The sediment load delivered to the reservoir from its filling 2002 to 2015 was estimated in 6,682,704 m 3 (16,706,761 Mg) (density of 2.5-Mg m-3) which value corresponded to 2.6 % of storage capacity (water plus sediment) in 14 years. These results are strategic since to become feasible identifying priority areas for soil and water conservation practices as well as useful information for water resources planning and management in the studied basin.

Estratégia Metodológica para Zoneamento pelo Potencial de Perda de Solo na Bacia Hidrográfica Cachoeira Cinco Veados, RS-Brasil

“…A erosão do solo, particularmente devido à perda de solo, é preocupante face à redução na capacidade produtiva do solo, aumento do assoreamento de recursos hídricos e redução da qualidade da água. Estudos sobre erosão do solo envolvem a quantificação da erodibilidade K do solo no campo sob chuva natural e o desenvolvimento de nomogramas para solo subtropical (Cassol et al 2018) ou em condições de laboratório (Thomaz e Fidalski, 2020), fator erosividade R (Avanzi et al, 2019) e uso e manejo C e práticas conservacionistas P da USLE , monitoramento do impacto do uso do solo sobre a produção de sedimentos em bacias hidrográficas para identificação de fontes de sedimentos (Rodrigues et al, 2018;Valente et al, 2020Valente et al, , 2021 ou pagamento por serviços ambientais (Bispo et al, 2020), efeito de plantas de cobertura na erosão do solo (Beniaich et al, 2020), práticas de manejo e relação com perda de solo, água e nutrientes (Reichert et al, 2019), perda do solo como indicador de risco à desertificação (Rios et al, 2020), fontes de sedimentos e volume erodido em voçorocas (Cândido et al, 2020), erosão em áreas degradas (Siqueira Junior et al, 2019), relação posição relevo solo com erosão e propriedades do solo (Almeida et al, 2019), e modelagem hidrossedimentológica em bacias hidrográficas (Mauri et al, 2020;Ebling et al, 2021). Além disso, a erosão tem clara relação com a qualidade da água (Becker et al, 2009;Kaiser et al, 2015), sendo necessária a identificação de fontes de poluição (Bastos et al, 2021) e com o balanço hídrico em bacias hidrográficas (Reichert et al, 2017;Ferreto et al, 2020.…”