Overview

Reservoirs are used for multiple purposes, typically a combination of water supply, flood control, hydropower generation, recreation, and environmental enhancement. A major element of utilizing reservoirs – and dams – for flood control, is the importance of the ‘guide curve’, which sets limits on the amount of water which can be safely stored at different times of the year. The risk of a flood event varies seasonally, so many guide curves also need to adapt to the season. The guide curve is typically established through weather and water forecasting, which has significantly improved over the last 50 years.

Guide curves are traditionally based on seasonal expectations and, in some cases, have informed the release of water ahead of storms to minimize flood risk – only to face water shortages during dry seasons. As weather forecasting systems have improved, reservoir operators have developed procedures for utilizing the forecasts to update the guide curves. FIRO builds on these modern forecasting improvements to allow reservoir operators to adjust operations more dynamically, helping to save stormwater oversupply when it is safe to do so and store it for dry seasons.

Seven Oaks FIRO

The local Seven Oaks Dam was originally constructed for flood risk management but is not authorized to capture water specifically for groundwater recharge. Although the existing operation of the dam provides some incidental water conservation benefits, it is possible to safely conserve more water through improved forecasting techniques.

The Seven Oaks FIRO Steering Committee is currently overseeing studies evaluating how FIRO can:

• Optimize dam operations
• Improve water conservation
• Maintain required flood safety expectations
• Support downstream habitats

In studies being conducted at the dam, FIRO is being explored as an option to help maximize groundwater recharge and downstream habitats while ensuring flood risk requirements are still being met. One FIRO study is evaluating how strategically managing releases from the dam combined with downstream channel modifications could help restore alluvial fan habitat for endangered species.

Atmospheric Rivers

FIRO is further being utilized to assess if forecasts of atmospheric rivers (AR) can be used to inform flexible reservoir operations at the Dam. Atmospheric rivers are long, narrow bands of concentrated water that can produce massive amounts of rain or snow when they make landfall. In the winter of 2022-2023, 17 atmospheric rivers affected California and produced most of the snow at Big Bear and over 14 inches of rain in the Santa Ana Basin. Accurately predicting the location, duration and runoff volume anticipated from atmospheric rivers is foundational to FIRO.

FIRO at Seven Oaks Dam is a collaborative research and operations partnership consisting of an interdisciplinary team of scientists, water managers, dam operators, and environmental experts. Water management needs inform the research required to optimize operations of the dam and results of this research are used for improving water conservation, managing flood risk, and improving downstream habitat.

Challenges

San Bernardino Valley Municipal Water District is responsible for the storage and distribution of a reliable water supply. Dams and reservoirs are used to mitigate flood events, generate clean hydropower, and ensure water availability in dry seasons. As the region faces increasing demands for water supply due to droughts, growing populations, and water scarcity, ensuring there is a dependable water supply for generations to come has become increasingly important.

Increases in climate variability and projected climate change are further challenging the assumptions used to design and operate existing dams and reservoirs. More frequent and severe floods and droughts are likely and adapting to this new paradigm of climatic uncertainty and extremes will require new approaches to water management, including more efficient operation of our existing dams and reservoirs.

FIRO represents a modern approach to reservoir management by using improved science, forecasting, and collaboration to better manage the water supply, reduce flood risk, and protect downstream ecosystems.

For more information on FIRO, visit the Center for Western Weather and Water Extremes website or contact Greg Woodside at GregW@SBVMWD.com.