Drought Assessment in the São Francisco River Basin Using Satellite-Based and Ground-Based Indices

The São Francisco River Basin (SFRB) plays a key role for the agricultural and hydropower sectors in Northeast Brazil (NEB). Historically, low part of SFRB, people have to cope with strong periods drought. However, there are incipient signs increasing drought conditions upper middle parts where its main reservoirs (i.e., Três Marias, Sobradinho, Luiz Gonzaga) croplands located. Therefore, assessment impacts extreme events SFRB is vital importance develop appropriate mitigation strategies. These characterized by widespread persistent dry long-term on water resources rain-fed agriculture. purpose this study provide comprehensive evaluation terms occurrence, persistence, spatial extent, severity, streamflow soil moisture over different time windows between 1980 2020. Standardized Precipitation-Evapotranspiration Index (SPEI) Streamflow (SSI) at 3- 12-month scales derived from ground data were used as benchmark indices. self-calibrating Palmer Drought Severity (scPDSI) Soil Moisture Ocean Salinity-based Water Deficit (SWDIS) assess Storage (WSDI) Groundwater (GGDI) both Gravity Recovery Climate Experiment (GRACE) hydrological SWDISa WSDI showed best performance assessing droughts across whole SFRB. A drying trend an annual scale south regions was evidenced. An expansion area under observed only during southern hemisphere winter months JJA). marked depletion groundwater levels concurrent increase content most severe conditions, indicating intensification abstraction irrigation. results could be useful guide social, economic, resource policy decision-making processes.