Enhancing Ensemble Seasonal Streamflow Forecasts in the Upper Colorado River Basin Using Multi-Model Climate Forecasts

CRB operational seasonal streamflow forecasts are produced using ESP, which represents climate using an ensemble of meteorological sequences of historical temperature and precipitation, but do not typically leverage additional real-time subseasonal-to-seasonal climate forecasts.

Any improvements to streamflow forecasts would help stakeholders who depend on operational projections for decision making. We explore incorporating climate forecasts into ESP through variations on an ESP trace weighting approach, focusing on Colorado River unregulated inflows forecasts to Lake Powell. The k-nearest neighbors (kNN) technique is employed using North American Multi-Model Ensemble one- and three-month temperature and precipitation forecasts, and preceding three-month historical streamflow, as weighting factors.