Water Balance In Hapic Cambisols Under Forest And Pasture In The Bonfim Watershed: Mountainous Region Of Rio De Janeiro State

Abstract

Objective: To estimate the water volumes of the main components of BH in a Haplic Cambisol in forests and pastures in the Bonfim River basin, mountainous region of RJ.   Theoretical framework: The water balance (BH) accounts for the volumes of water input and output in a given space (Haplic Cambisols under forests and pastures). Method: The study period was 01/01/2000 and 12/31/2019. The HYDRUS-1D model was used to estimate water volumes in BH. Pedotransfer functions were used to determine the physical water parameters of water retention and conduction in the soil. The daily precipitation and evapotranspiration data were considered upper boundary conditions, and the lower boundary conditions were considered free drainage. Water absorption by the roots was considered as the additional factor (Sink factor) in the soil water mass balance.   Results and conclusion: The average annual precipitation was 1462 mm and the potential evapotranspiration was 1026 mm. In lhe area under pastures: 83%, 7% and 9% of the total precipitated and percolated, transpired and evaporated, respectively. In areas under forests: these values were 43%, 51% and 6%. In the dry season, evapotranspiration was 20% of the total precipitation in the forest area and 8% in the pasture areas. Percolation in the dry season was 17% of the total precipitation in the pasture and 7% in the forest. In the rainy season the percolated values were 66% in the pasture and 36% in the forest.   Implications of the research: Knowing the volumes of water in the components of the BH can help in decisions regarding the organization of land use and cover systems in basins of the Atlantic Forest biome. Changing soil use and cover systems alters the volumes of water percolated or evapotranspired.   Originality/value: Estimating the water volumes in the BH components in pasture and forest allows predicting the effects of climate change and land use and their consequences.