Lake Powell is a major reservoir responsible for providing water
resources throughout the Colorado River Basin. Here we develop a hybrid
model to perform 1-4 month forecasts of the inflow to Lake Powell.
First, observational data are used in early December for a binary
prediction of high- or low-flow based on peak monthly inflow or
April-July inflow, and our prediction is much better than the Colorado
Basin River Forecast Center (CBRFC)’s forecasts for the 1982-2016 study
period. Second, we calibrate the NCEP Climate Forecast System seasonal
forecasts of temperature, precipitation, and snow mass, and use them to
perform 1-4 month inflow prediction through a regression equation, with
the coefficients determined for the high- and low-flow years separately.
Our early April forecasts for the critical April-July inflow are better
than those of the CBRFC from 1982-2016. Sensitivity tests have also
demonstrated the value of including snow mass in our prediction.