Disentangling the historic and future impacts of land use changes and climate variability on the hydrology of a mountain region in Brazil

Abstract

Global changes in land use and land cover (LULC) and climate are expected to have profound impacts on water dynamics, which are key for human wellbeing. However, we still lack understanding of how changes in climate patterns and LULC are likely to interact and govern the hydrology at the watershed level in tropical regions in the future. Here we assessed the contribution of changes in weather patterns and LULC on the hydrology of a watershed in southeast of Brazil between 1990 and 2015 using the SWAT model. In addition, we explored the likely impacts of two contrasting LULC scenarios (Green Road versus Fossil Fuel) on the hydrology in 2045 under the Representative Concentration Pathway 8.5. Between 1990 and 2004 and 2005–2015 the watershed witnessed an increase in precipitation and streamflow, in combination with an expansion of forest cover and coffee production. While surface runoff (+5.2 mm year−1) and water yield (+252 mm year−1) increased, soil water (−24.6 mm year−1) and evapotranspiration (−15.7 mm year−1) decreased. The analysis indicated that changes in climate patterns are the main drivers of historical water dynamics in the region. Compared with Fossil Fuel scenario, the increase in forest area in the Green Road scenario will lead to a decrease in surface runoff and consequently in water yield, favouring water infiltration and soil erosion control, and buffer against extreme precipitation events. Therefore, the socioeconomic and public policies underlying the Green Road scenario that favour the expansion of forests can direct sustainable future water management.