Estimating Benefits of Forecast-Informed Reservoir Operations (FIRO): Lake Mendocino Case-Study and Transferable Decision Support Tool

Forecast-Informed Reservoir Operations (FIRO) enables modern weather forecasting technology to be incorporated into Water Control Plans. FIRO provides water managers with more lead time to selectively retain or release water from reservoirs in anticipation of droughts or floods. Managing reservoirs with improved forecasts can optimize benefits such as water supply and fisheries without impairing flood risk management.

FIRO viability at Lake Mendocino was assessed according to five management scenarios and evaluated using 16 metrics. Through detailed hydrologic engineering analysis, the difference in water availability was calculated comparing baseline operations and the FIRO alternatives. Based on the evaluation criteria and implementation considerations, the Modified Hybrid alternative was selected and Ensemble Forecast Operations was designated as a reach goal.

The benefits assessment considered the water availability difference between baseline and FIRO operations with respect to recreation, hydropower, municipal and industrial water supply, agricultural water supply, and fisheries. To calculate the recreation benefit, daily use values were applied to estimated recreational activity at Lake Mendocino. Hydropower benefit was calculated by applying regional retail electricity prices to the increased electricity generated under FIRO operations. Municipal and industrial water supply benefit was determined by quantifying changes in consumer surplus due to an increase in water reliability. Changes in consumer surplus were determined by estimating demand curves for water usage and using price elasticity of demand. Agricultural water supply benefits were calculated as annual avoided losses and used the residual imputation method. The least-cost method was used to monetize fisheries benefit of FIRO based on changes in downstream flow and water temperature.

Results are being integrated into the Lake Mendocino FIRO Final Viability Assessment, which will be finalized by December 2020. A decision support tool (DST) will allow users to input data from other FIRO projects to predict benefits and inform tradeoff decisions.

This presentation will share results of the economic assessment, preview the DST, and describe a transferability test case at Prosser Reservoir in the Truckee River Basin.