The deforestation of areas of land affects the state of the streams and affects the amount of water in the atmosphere. Over half of the native vegetation has been removed in the watershed of the Araguaia River in east-central Brazil.
Without as much vegetation, there is less evapotranspiration which means there is more moisture in the ground rather than in the air. Most of the deforestation is due to the high demand for agricultural uses. This land is more useful to a person trying to make a living when they can grow crops and raise cattle. Despite the economical advantages to using land for agricultural purposes, the ecosystem has been designed to have dense vegetation and it is unnatural to change one of the ecosystems most identifiable and important characteristics. Water runoff, river discharge, erosion and sediment fluxes are the most common hydrological, geomorphological, and biochemical issues coming from the mass deforestation.
Coe, Latrubesse, Ferreira, & Amsler. (2011). The effects of deforestation and climate variability on the streamflow of the Araguaia River, Brazil. Springer Science Business Media.