Water productivity monitoring by using geotechnological tools in contrasting social and environmental conditions: Applications in the São Francisco River basin, Brazil

Abstract We used the SAFER (Simple Algorithm for Evapotranspiration Retrieving) algorithm together with the Monteith's RUE (Radiation Use Efficiency) model, for large-scale water productivity assessments in different social and environmental conditions of the Sao Francisco River sub basins, Brazil, by coupling remote sensing parameters from MODIS images and a net of agrometeorological stations, during the year 2016. Variations on actual evapotranspiration (ET) and biomass production (BIO) among ecosystems and sub basins were strongly detected, affecting the water productivity based on ET (WP = BIO/ET). The mean ET daily rates were 2.1 mm d−1 for both, Forest Zone (FZ) and Savanna (SV), and 1.3 mm d−1 for Caatinga (CA), while regarding BIO they were 67, 68 e 33 kg ha−1 d−1, for FZ, SV, and CA, respectively resulting in corresponding average WP values of 2.6; 2.5, and 1.7 kg m−3. The modelling by using the MODIS reflectance product together with gridded weather data presented operational applicability for monitoring water and vegetation dynamics at a 16-day period and at a 250 m spatial resolution along the year, under conditions of distinct water availability. The satisfactory results highlighted the suitability of geotechnological tools to subsidize the rational natural resources management on large scales in societies with different environmental vulnerabilities.