Ho (2026) Fielding floods for farms and (low) flows : the potential benefit of repurposing small flood reservoirs for drought protection

Identification

• Journal: Repository KITopen (Karlsruhe Institute of Technology)
• Year: 2026
• Date: 2026-01-01
• Authors: Sarah Ho
• DOI: 10.5445/ir/1000189943

Research Groups

• Center for Disaster Management and Risk Reduction Technology (CEDIM), Karlsruher Institut für Technologie (KIT)
• Institut für Wasser und Umwelt (IWU), Karlsruher Institut für Technologie (KIT)

Short Summary

This study investigates the potential of repurposing small flood reservoirs in temperate regions for drought protection, specifically for streamflow supplementation and agricultural irrigation, while maintaining their flood control functions. It demonstrates that significant water supply benefits can be achieved, particularly for agriculture, without increasing flood risk, even under uncertain forecast conditions.

Objective

• To explore the potential water supply benefits of repurposing small flood reservoirs for drought protection (streamflow supplementation and irrigation demand) in temperate regions, while simultaneously preserving their flood protection functions.

Study Configuration

• Spatial Scale: 30 small flood reservoirs in the German state of Baden-Württemberg.
• Temporal Scale: Focus on the years 2017-2020, including the landmark 2018-2020 drought years. Models were tested under perfect-knowledge conditions and uncertain forecasts, with implications for future climate change scenarios.

Methodology and Data

• Models used: Operational models were developed to represent the dual-purpose operation of repurposed flood reservoirs, simulating streamflow supplementation and agricultural irrigation demand. These models were tested under both perfect-knowledge conditions and conditions with uncertain hydrological forecasts.
• Data sources: Inflow data, agricultural irrigation demand data, and hydrological forecasts (for uncertain conditions).

Main Results

• Under perfect-knowledge conditions, 12 of the 30 tested reservoirs could alleviate at least 70% of drought conditions for streamflow supplementation, with no increase in flooding.
• For irrigation demand under perfect-knowledge conditions, 20 of the 30 tested reservoirs could provide at least 70% of the needed water during the 2018-2020 drought years without increasing flooding.
• When operating under uncertain forecasts, most reservoirs were still able to provide tangible benefits (> 40%) for either use case.
• Performance decay from perfect-knowledge to forecasted conditions was primarily explained by flood incidence and the timing of flood predictions, rather than common forecast quality metrics.
• The most successful operating rules involved aggressive water storage and holding water as long as safely possible.
• Overall, repurposing flood reservoirs offers high potential water supply benefits, especially for agriculture, and can be operated without increasing flood risk.

Contributions

• Explores the novel concept of repurposing small flood reservoirs for drought protection in temperate regions, an area previously underexplored.
• Develops and applies operational models for dual-purpose reservoir management, integrating flood protection with drought mitigation strategies (streamflow supplementation and irrigation).
• Quantifies the potential benefits of such repurposing under both ideal (perfect-knowledge) and realistic (uncertain forecast) conditions.
• Demonstrates that significant water supply resilience can be achieved without compromising existing flood protection functions.
• Provides foundational tools and insights for individual reservoir analyses, contributing to informed discussions on increasing water supply resilience in a changing climate.

Funding

Not explicitly mentioned in the provided text.

Citation

@article{Ho2026Fielding,
  author = {Ho, Sarah},
  title = {Fielding floods for farms and (low) flows : the potential benefit of repurposing small flood reservoirs for drought protection},
  journal = {Repository KITopen (Karlsruhe Institute of Technology)},
  year = {2026},
  doi = {10.5445/ir/1000189943},
  url = {https://doi.org/10.5445/ir/1000189943}
}