Ho et al. (2026) Forecast-based operation of repurposed small reservoirs for floods, farms, and (low) flows

Identification

• Journal: Hydrology and earth system sciences
• Year: 2026
• Date: 2026-08-03
• Authors: Sarah Ho, Robert J. Lang, Uwe Ehret
• DOI: 10.5194/hess-30-4847-2026

Research Groups

• Institute for Water and Environment – Hydrology, Karlsruhe Institute of Technology
• Center for Disaster Management and Risk Reduction Technology (CEDIM), Karlsruhe Institute of Technology
• HYDRON Ingenieurgesellschaft für Umwelt und Wasserwirtschaft GmbH

Short Summary

This study investigates the potential benefits of repurposing small flood reservoirs for drought protection when operating under forecasts, particularly under the constraint that the reservoir's flood protection function should not be compromised. The results show that many small flood reservoirs can maintain benefits above 40% even when optimized to operate under forecasts.

Objective

• Determine if the uncertainty introduced by using forecasts for decision-making significantly decreases the performance of repurposed small reservoirs' operation.
• Identify patterns in the relationship between forecast accuracy and optimal performance between the perfect knowledge and forecasting operations.
• Identify patterns in optimal reservoir operation rules, under the constraint that flood protection should not be compromised.

Study Configuration

• Spatial Scale: Small-to-midsize (less than 5 million m3) flood reservoirs in southwest Germany.
• Temporal Scale: Hourly resolution for streamflow forecasts and inflow time series.

Methodology and Data

• Models used: Large Area Runoff Simulation Model (LARSIM), COSMO-DE, COSMO-D2, and ICON-D2 forecasting products.
• Data sources: Historical weather forecast datasets archived by the flood forecasting center of Baden-Württemberg, crop cover and soil texture maps.

Main Results

• Many small flood reservoirs can maintain benefits above 40% even when optimized to operate under forecasts.
• High rates of hits, false alarms, and misses (HFM) in forecast accuracy can explain the largest decreases in performance.
• Optimal operation rules tend to be those that most closely mimic perfect knowledge operation.

Contributions

• This study provides new insights into the potential benefits of repurposing small flood reservoirs for drought protection when operating under forecasts.
• The results have implications for water management and policy-making, particularly in regions where climate change is expected to increase the frequency and severity of droughts.

Funding

• Not specified.

Citation

@article{Ho2026Forecastbased,
  author = {Ho, Sarah and Lang, Robert J. and Ehret, Uwe},
  title = {Forecast-based operation of repurposed small reservoirs for floods, farms, and (low) flows},
  journal = {Hydrology and earth system sciences},
  year = {2026},
  doi = {10.5194/hess-30-4847-2026},
  url = {https://doi.org/10.5194/hess-30-4847-2026}
}