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- Title
Enhanced Modulation of Streamflow Flash Droughts by Reservoir Operations in India.
- Authors
Singh, Rajesh; Mishra, Vimal
- Abstract
Streamflow flash droughts (SFDs) occur due to a rapid decline in streamflow and cause major challenges associated with water availability for downstream ecosystems, hydropower generation, and irrigation water demand. Human interventions such as reservoir operations and reservoir storage can considerably influence streamflow variability. However, the crucial role of dams/reservoirs on the occurrence of SFDs in India remains unexamined. Using a combination of hydrological and hydrodynamical models, we examined the role of reservoirs on SFDs in India during 1971–2020. Reservoirs play a considerable role in the occurrence of SFDs during the summer monsoon season (June‐September) in India. The frequency and severity of SFDs in the presence of reservoirs are substantially lesser than in the absence of them. In addition, high and low antecedent reservoir storage conditions before meteorological flash droughts (MFDs) do not support the rapid decline of streamflow (i.e., SFDs) downstream of reservoirs, while the medium reservoir storage conditions prior to MFDs favor the development of SFDs. Similar to conventional (or long‐term) streamflow droughts (SDs), SFDs are more frequent in the El Nino phase than in the La Nina phase. Unlike the long‐term streamflow droughts, the implementation of dams considerably reduces the frequency of SFDs during both the negative and positive phases of El Nino Southern Oscillation. Overall, our findings demonstrate the considerable role of human interventions in flash drought occurrence, as SFDs are triggered by MFDs but modulated by reservoir storage and operations. Plain Language Summary: A rapid decline in streamflow poses significant challenges to water availability in downstream regions. Human interventions, particularly associated with dam operations and reservoir storage, can profoundly affect streamflow variability in the downstream of reservoirs. However, the impact of reservoirs on a rapid decline in streamflow (i.e., streamflow flash drought (SFD)) in India has not been examined. Using hydrological and hydrodynamical models, we investigated the role of dams/reservoirs on the occurrence of SFDs in India from 1971 to 2020. We find that reservoirs play a substantial role in reducing the frequency and severity of SFDs during the summer monsoon. High and low reservoir storage before the occurrence of a considerable precipitation deficit in short duration (meteorological flash droughts (MFDs)) in the upstream catchment restricts the occurrence of SFDs. However, medium reservoir storage conditions support the occurrence of SFDs. These findings highlight the crucial role of human interventions, specifically reservoir storage and operations, in mitigating SFDs triggered MFDs. Key Points: Examined the role of dams in modulating flash and conventional streamflow droughts in 36 catchments in IndiaDams/reservoirs decrease the frequency and severity of streamflow flash droughts (SFDs) during the summer monsoon seasonDams modulate the influence of climate variability more effectively on SFDs compared to conventional streamflow droughts
- Subjects
INDIA; EL Nino; STREAMFLOW; RESERVOIRS; LA Nina
- Publication
Water Resources Research, 2024, Vol 60, Issue 6, p1
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2024WR037036