Multi-Year Forecasts of Colorado River Water Supply

Perspective

Our forecasts based on ocean precursors suggest that low water supply conditions will persist through 2028. In particular, our hybrid approach (i.e., combining statistical and dynamical models) predicts reduced water availability in 2028, highlighting continued drought risks. After 2028, dynamical models predict a phase shift in ocean precursors over the North Pacific and Tropical Atlantic (Fig. 2), indicating a potential end to the persistent drought. While our forecasts did not capture the anomalously wet year in 2023 due to short-term atmospheric disturbances, large-scale ocean conditions continue to favor drought. Therefore, it remains critical to prepare for multi-year drought risks over the coming years.

Figure 1 Multi-Year Forecasts of Colorado River Water Supply. The blue and red lines represent the observed and forecasted water supply at Lees Ferry, Arizona, respectively. Observations are provided by the Bureau of Reclamation, and forecasts are based on ocean precursors. Thin lines indicate annual values, while thick lines show three-year averages, both based on the water year.

Ocean Precursor Forecast

Figure 2 Multi-Year Forecasts of Ocean Precursors. (a) Observed and forecasted Colorado River water supply (as in Figure 1), extended to include 2028 forecasts based on a combination of ocean precursors: the North Pacific precursor derived from North American Multi-Model Ensemble (NMME) forecasts and the Tropical Atlantic precursor derived from observational data. (b) North Pacific precursor from three observational sources (gray lines) and their average (black line), along with NMME forecasts (colored lines). (c) Tropical Atlantic precursor from three observational sources (gray lines) and their average (black line), along with NMME forecasts (colored lines). Colored crosses indicate individual model forecasts, and the red line denotes the multi-model ensemble mean.

References

Chikamoto, Y., S.-Y. Simon Wang, M. Yost, L. Yocom and R. R. Gillies (2020): Colorado River water supply is predictable on multi-year timescales owing to long-term ocean memory. (Nature) Communications Earth & Environment, 1, 26, doi:10.1038/s43247-020-00027-0.
Plucinski, B., Y. Sun, S.-Y. Wang, R. R. Gillies, J. Eklund, and C.-C. Wang (2019): Feasibility of Multi-Year Forecast for the Colorado River Water Supply: Time Series Modeling. Water, doi:10.3390/w11122433.
Wang, S.-Y., R. R. Gillies, O.-Y. Chung, and C. Shen (2018): Cross-Basin Decadal Climate Regime connecting the Colorado River and the Great Salt Lake. Journal of Hydrometeorology, doi:10.1175/JHM-D-17-0081.1.

This utility has been developed in partnership with the Bureau of Reclamation for the WaterSMART project.