Impact Of Reservoir Storage On Propagation From Meteorological To Hydrological Drought

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https://doi.org/10.1016/j.jhydrol.2026.136061 <-- shared paper

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H/T Dr Ajay Gupta

“🌍 Why is this important?

While reservoirs are widely recognized for mitigating drought impacts, their role in controlling how drought propagates through the hydrological cycle has remained largely unexplored. In this study, [the authors] investigate how reservoir storage influences the transition of drought from meteorological to agricultural to reservoir to streamflow drought across the semi-arid Krishna River Basin, India.

🔍 THIS STUDY ADDRESSES TWO KEY RESEARCH QUESTIONS:

✅ How do drought propagation time (initiation, peak, and termination) change from meteorological to agricultural, reservoir, and streamflow droughts across different timescales and threshold values?

✅ How does reservoir storage influence drought propagation between upstream and downstream reservoirs using the Downstreamness concept?

📌 KEY FINDINGS:

🔹 Drought propagation differs substantially across drought types because each component of the hydrological system responds at different rates.

🔹 Reservoirs significantly delay the propagation of drought by buffering water deficits, particularly between agricultural and streamflow drought.

🔹 Mild and moderate upstream reservoir droughts rarely propagate downstream, whereas severe upstream droughts consistently transmit downstream, leading to longer duration, greater severity, and delayed onset.

🔹 The downstreamness analysis reveals dynamic shifts in water storage between upstream and downstream reservoirs throughout drought development and recovery, providing valuable insights for reservoir operation and basin-scale drought management…”

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“HIGHLIGHTS

• Reservoir storage impact on drought propagation from meteorological-to-hydrological drought.

• Drought propagation timeframe: initiation, peak and termination are checked.

• Impact assessment using hydrological connection: upstream to downstream reservoirs.

• Severe upstream droughts propagate downstream with increased duration and severity.

• During drought periods water-storage concentration shifts from downstream to upstream.

ABSTRACT: Reservoirs are central to moderating and mitigating drought, yet their influence on drought propagation through socio–hydrological systems remains under–examined. This study quantifies how reservoir storage shapes the progression of meteorological, agricultural, reservoir, and streamflow droughts across 11 major reservoirs in the semi–arid Krishna River Basin, India (2000–2019). Using the SPEI, SSMI, SRSI, and SSI indices, we estimate initiation, peak, and termination lags at multiple timescales and thresholds. Reservoir influence is further assessed using the Downstreamness concept to capture upstream–downstream hydrological connectivity.

Results show that drought propagation varies markedly across indices due to contrasting system response times. Meteorological–to–agricultural drought propagates rapidly at short timescales, whereas agricultural–to–reservoir and reservoir–to–streamflow droughts exhibit longer delays linked to reservoir buffering. Termination is most variable for agricultural–to–reservoir drought and shortest for reservoir–to–streamflow drought, reflecting rapid downstream recovery once reservoirs refill. Upstream–downstream analysis reveals that mild and moderate upstream reservoir droughts rarely propagate, but severe upstream droughts consistently transmit downstream, with longer duration, greater severity, and delayed onset. Downstreamness dynamics further show shifting patterns of water retention over the drought cycle, underscoring the importance of hydrological connectivity in shaping drought outcomes.

These findings provide actionable insights for basin–scale water management, highlighting the need to incorporate reservoir connectivity and drought–severity thresholds into drought mitigation strategies. The approach offers transferable value for other semi–arid basins facing similar multi–stage drought propagation challenges…”

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