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

Abstract

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

Microwave remote sensing for agricultural drought monitoring: Recent developments and challenges

“…Anomalies and percentiles (Champagne et al, 2011;Nicolai-Shaw et al, 2017;van Hateren et al, 2021;Vroege et al, Soil Moisture Deficiency Index (SMDI) (Pablos et al, 2017;Xu et al, 2018;Fang et al, 2021) Soil Water Deficit Index (SWDI) (Martínez-Fernández et al, 2016Mishra et al, 2017;Pablos et al, 2017;Paredes-Trejo and Barbosa, 2017;Bai et al, 2018;Fang et al, 2021;Paredes-Trejo et al, 2021;Zhou et al, 2021;Cao et al, 2022;Chatterjee et al, 2022;Wu et al, 2022)…”

Challenges of defining the floodplain through the “mean ordinary flood line” approach using remote sensing in Brazil: a case study of the São Francisco River

“…The legal and technical aspects of the MOFL make it difficult to be revised over short periods of time. If a drying trend could be observed in less that 40 years (Paredes-Trejo et al, 2021), should the MOFL be based on a shorter period of analysis? Given these trend, can the land within the MOFLs be sustainably exploited or will over exploitation threaten even more the land of degradation and desertification?…”

Assessment of Wet and Dry Spells Over North Western Zone of Tamil Nadu Using WASP

“…There are four components that exhibits drought occurrence, its nature and severity. Those are rainfall, ground water level, water storage in reservoirs and the last is the crop condition [2]. The foremost is the rainfall, proper understanding about the distribution and probabilities of occurrence of extreme events is essential for crop planning as well as designing of water storage structures [3].…”