Reservoir Operators React to Uncertainty in Snowmelt Runoff Forecasts: Fid-Bau Portal

Reservoir Operators React to Uncertainty in Snowmelt Runoff Forecasts

Stillinger, Timbo / Costello, Christopher / Bales, Roger C. / Dozier, Jeff

Over 1 billion people rely on snow and ice for their water supply, and in many areas, reservoirs store the water after the snow melts. Deciding when to release water depends partly on forecasts of how much more rain and snowmelt will flow into the reservoirs. Often these forecasts express uncertainty, reporting a range of possible flows. We examined how those responsible for releasing water from reservoirs respond to forecasts using a case study of the historical record of past forecasts and water releases in California’s Sierra Nevada. Results from a panel data model with fixed effects showed that these water managers hedge their bets against the possibility of less water than forecasted. Greater uncertainty in a forecast was associated significantly with a reduced amount of released water, and the effect of uncertainty on releases declined as the forecast volume increased (adjusted $R^{2} = 0.70$ , $F$ -test $p ≪ 0.001$ ). Our results suggest that increasing water managers’ confidence in upcoming flows by reducing forecast uncertainty would allow more water to be released from reservoirs earlier in the year, without the need for direct coordination with these managers.