Spatial modeling of evapotranspiration and water productivity in the outcrop area of the Guarani Aquifer in São Paulo State between 2013 and 2015

Abstract

This research aims to evaluate the spatial and temporal distribution of of water productivity (evapotranspiration and biomass production) for São Paulo Guarani Aquifer Outcrop between 2013 and 2015, in order to evaluate the impact of the drought of 2014 in the region. The algorithm used to calculate evapotranspiration was SAFER (Simple Algorithm For Evapotranspiration Retrieving) and the Monteith equation to estimate the parameters of biomass production. Were used data from agrometeorological stations and digital images without clouds from MODIS satellite of the same julian days between 2013 and 2015. In average values, for all the São Paulo area of the outcrop of the Guarani aquifer, there was a decrease in evapotranspiration and biomass production in the drought years (2014-2015). Water productivity, when taken in reference to a historical series that allows a trend analysis, is an indicator of water stress of vegetation and crops. The significant decrease in evapotranspiration in 2014 and 2015 is an evidence of impacts on aquifer recharge and decrease in the water table. Evidence was found that drought had a greater impact in the rural region north of the outcrop of the Guarani Aquifer (Ribeirão Preto region) compared to the Paranapanema region, being a possible explanation for this the fact that the first one has predominance of sugarcane and the second one of Eucalyptus. This spatial information generates subsidies for decision making in regional environmental management.