ABSTRACT
Minas Gerais state, Southeast Brazil, has experienced some cases of drought, while arising rainfall water excess in some areas and periods of specific years. These scenarios demand large-scale water balance studies to subsidize water resource policies. The reflectance bands from the MOD13Q1 Moderate Resolution Imaging Spectroradiometer (MODIS) product were used together with weather data to acquire drought indicators in the state, during the years from 2012 to 2015, emphasizing the main agricultural growing regions, North, Northwest, and Minas Triangle, to access agricultural drought hazard risks and possibilities of rainfall water storage for mitigating water scarcity. Precipitation (P) and reference evapotranspiration (ET0) data from 36 weather stations were interpolated, and for acquiring the actual evapotranspiration (ET), the SAFER algorithm was used. Two drought indicators applied for the large-scale analyses were the water balance deficit (WB d = P−ET) and the evapotranspiration ratio (ET r = ET/ET0). Higher WBd values resulted from the mid of October to the end of December, but with the largest ET r values happening between March and May, a period of the year presenting the lowest drought agricultural hazards. According to the ET r values, the soil moisture storage showed a gap in relation to the climatic WB d indicator, because of the lapse time for the crop root zones, recovering their water-retention capacities. Considering all studied years, ET attended the atmospheric demand by 50%, 53%, and 61% in the agricultural growing regions of North, Northwest, and Minas Triangle. The potential for drought monitoring at the 16-day time scale by combining weather data and the reflectance MODIS product was demonstrated.
