2016 Salt Lake County Watershed Symposium

Leaving the Past Behind: Water Supply Forecasting in the Great Basin
The National Oceanic and Atmospheric Administration’s (NOAA’s) Colorado Basin River Forecast Center (CBRFC) provides forecasts of water supply conditions to resource managers throughout the Eastern Great Basin regions using Ensemble Streamflow Prediction (ESP) methods that are largely driven by historical observations of temperature and precipitation. Currently, the CBRFC does not incorporate climatic information, such as teleconnections (e.g., the El Niño Southern Oscillation [ENSO]), into the development of its streamflow ensembles; further, as the impacts of climate change are realized, the past may no longer be representative of future conditions. To address these issues, the CBRFC is investigating the incorporation of a Stochastic Weather Generator (SWG) developed by the University of Colorado. Additionally, numerous agencies issue climate outlooks that describe the probability that a region with experience warmer, normal, or cooler conditions with regards to temperature and wetter, normal, or drier conditions with regards to precipitation. Research published by the University of Colorado has shown that a SWG weighted by probabilities related to the ENSO may improve forecast skill in the San Juan River Basin, as well as other regions outside of the Colorado River Basin. In this study, the SWG is applied within the Great Basin and weighted using climate probabilities developed by the National Weather Service’s Climate Prediction Center. The ensemble of streamflow events developed using the SWG is then compared to historical ensembles used in the forecast of water supply over the region.