Wildfires and their impact on the water supply of a large neotropical metropolis: A simulation approach

Hydrological models are powerful tools to simulate the behavior of the water cycle in terrestrial systems and their water interface, including modifications resulting from anthropic activities. In such environments the water stocks depend heavily on the vegetation cover and the ecosystem services derived from it, as part of the interaction soil-plant-topography. Wildfires are disturbances capable of breaking the foundations of these delicate systems. We used the Soil and Water Assessment Tool (SWAT) to simulate the effects of vegetation fires on drainage basins, on the water supply of one of the largest Brazilian urban agglomerations. The model was fed and calibrated with historical hydroclimatic series (calibration January 2001-December 2008, validation January 2009-December 2015). The adjusted model allows to predict the impacts of fire extension on infiltration and runoff, a valuable information for land management, aiming at protecting aquifer recharge. The model predicts a scenario of large range fluctuations characterized by pulsed floods in the rainy season and drought in the dry season. The loss of protective vegetation cover due to fire reduces infiltration and increases runoff. This compromises groundwater recharge, leading to high deficits in groundwater storage and reducing the baseline flow of headsprings.