Evaluating National Weather Service Seasonal Forecast Products in Reservoir Operation Case Studies

Monday, 15 December 2014
Ashley Nielson, National Weather Service Salt Lake City, Salt Lake City, UT, United States, Rebecca Guihan, University of Massachusetts Amherst, Civil and Environmental Engineering, Melrose, MA, United States, Austin Polebistki, University of Wisconsin Platteville, Department of Civil and Environmental Engineering, Platteville, WI, United States, Richard N Palmer, University of Massachusetts Amherst, Amherst, MA, United States, Kevin Werner, NOAA Seattle, Regional Climate Services, Seattle, WA, United States and Andrew W Wood, National Center for Atmospheric Research, Boulder, CO, United States
Forecasts of future weather and streamflow can provide valuable information for reservoir operations and water management. A challenge confronting reservoir operators today is how to incorporate both climate and streamflow products into their operations and which of these forecast products are most informative and useful for optimized water management. This study incorporates several reforecast products provided by the Colorado Basin River Forecast Center (CBRFC) which allows a complete retrospective analysis of climate forecasts, resulting in an evaluation of each product’s skill in the context of water resources management.

The accuracy and value of forecasts generated from the Climate Forecast System version 2 (CFSv2) are compared to the accuracy and value of using an Ensemble Streamflow Predictions (ESP) approach. Using the CFSv2 may offer more insight when responding to climate driven extremes than the ESP approach because the CFSv2 incorporates a fully coupled climate model into its forecasts rather than using all of the historic climate record as being equally probable. The role of forecast updating frequency will also be explored.

Decision support systems (DSS) for both Salt Lake City Parley’s System and the Snohomish County Public Utility Department’s (SnoPUD) Jackson project will be used to illustrate the utility of forecasts. Both DSS include a coupled simulation and optimization model that will incorporate system constraints, operating policies, and environmental flow requirements. To determine the value of the reforecast products, performance metrics meaningful to the managers of each system are to be identified and quantified. Without such metrics and awareness of seasonal operational nuances, it is difficult to identify forecast improvements in meaningful ways. These metrics of system performance are compared using the different forecast products to evaluate the potential benefits of using CFSv2 seasonal forecasts in systems decision making.