Forecasts and Planning Tools

Seasonal to Interannual Forecasts

Water Resources Forecasts

In collaboration with the Land Surface Hydrology Group at the University of Washington, the Climate Impacts Group (CIG) has developed experimental streamflow forecasting systems for the Columbia River and Snake River basins. There are currently two ways to access these forecasts:

Quasi-operational Western United States Streamflow Forecasts

These 12-month forecasts of monthly streamflow ensembles, spatial distributions of snow water equivalent, soil moisture, and runoff for major western U.S. river basins are updated in the last week of every month. Nowcasts of spatially-distributed snow water equivalent and soil moisture conditions are also provided.

• Geographical coverage, Pacific Northwest (PNW): 15 locations in the Columbia River and 20 locations in the Snake River
• Geographical coverage, rest of US: California, Colorado River basin, Great Basin, Upper Rio Grande
• Forecasting methods: Streamflow simulation using a macroscale hydrologic model, using (1) the Ensemble Streamflow Prediction (ESP, formerly Extended Streamflow Prediction) method conditioned on ENSO and PDO states, (2) ensemble forecasts downscaled from several climate models, and (3) ensemble forecasts based on the longer than 12-month lead-time Climate Prediction Center Outlooks.

Note: the forecasting methods and the form of publishing the forecasts are still in development.

One Year Lead Time Streamflow Forecast for the Columbia River at The Dalles

This forecast of monthly Columbia River streamflow at the Dalles (September-October) is typically made in June preceding the forecast water year and is only updated as necessary during the summer to reflect significant changes in climate conditions. This forecast is not updated during the winter.

• Geographical coverage, PNW: the Columbia River at The Dalles
• Forecasting methods: Streamflow simulation using macro-scale hydrological model initialized with current hydrologic conditions, driven by resampled historical meteorological data conditioned by forecasted ENSO conditions.

Note: because the method developed to support this forecast has been incorporated into the forecasts produced by (1), this individual forecast effort will be gradually phased out.

Application to Water Resources Management in the Columbia River Basin

A discussion of the potential use of long-range streamflow forecasts for water management and a retrospective assessment of the economic worth of forecasts for the Columbia River hydro system is presented in Hamlet and Lettenmaier (1999) and Hamlet et al. (2002).