Mitigating severe hydrological droughts in the Brazilian tropical high-land region: A novel land use strategy under climate change

Abstract

Severe droughts have significantly increased in frequency, magnitude, and intensity over the past decade, particularly impacting tropical and subtropical regions. Southeast Brazil exemplifies this trend, where severe hydrological droughts threaten the economy and society. We propose a novel approach to assess the impact of land use and climate change on severe hydrological droughts by integrating streamflow simulations with the Standard Hydrological Index (SHI), which is based on variations in water storage within the basin. To test our approach, the Lavras Simulation of Hydrology (LASH) model was applied to sixty-nine sub-basins in the upper Grande River basin, Southeast Brazil. We defined severe droughts as events where SHI ≤ −1.5, calculating threshold water storage (S_threshold) for the baseline period (1961–2005) to evaluate the impacts of land use and climate change scenarios. Land use scenarios were designed to maintain stable agricultural areas, while climate change scenarios (RCP4.5 and RCP8.5) were projected through 2060. The findings indicated that forest recovery significantly reduced severe hydrological drought frequency, whereas deforestation intensified it. Sub-basins altered by human activity showed more susceptibility to climate change. However, forested sub-basins were notably impacted by land use changes, mainly from pasture replacing Atlantic Forest. Highlighting deforestation as a critical driver for regional hydrological vulnerability, our method underscores the urgent need for effective land use management and conservation strategies of Atlantic Forest to mitigate the risk of severe droughts, regardless of the climate change pathways.