Woodson Lees Ferry WY flow forecast

This experimental streamflow forecast uses a machine learning (random forest) model trained on Reclamation annual natural flow for the Colorado River at Lees Ferry, AZ for water years 1921-2023 as the predictand. The predictors include:

• Pacific Decadal Oscillation (PDO) index, July-August-September average preceding the water year being forecast
• Atlantic Multidecadal Oscillation (AMO) index, July-August-September average preceding the water year being forecast
• Community Earth System Model - Large Ensemble (CESM-LE) forecasts of precipitation and minimum temperature, October through September average coinciding with the water year being forecast

For example, for the 2024 water year forecast (October 2023 - September 2024 total natural flow), PDO and AMO predictors are July 2023 through September 2023 monthly averages, and the CESM-LE precipitation and temperature predictors are October 2023 through September 2024 monthly averages. The random forest forecast is a 600-member ensemble.

The second plot below shows the 'variable importance' for each predictor over the 1921-2023 training period; each variable does add value (this is how the variables were selected), and AMO and PDO have the highest importance.