Use of Climate Information in Official Western US Water Supply Forecasts

摘要

Throughout the western US, the Natural Resources Conservation Service and cooperating agencies have produced long-lead seasonal volumetric water supply forecasts since the early 1900's. These statistical regression-based forecasts primarily rely on measurements of current snowpack and proxies of soil moisture such as antecedent streamflow and autumn precipitation. It has long been recognized that the largest source of forecast uncertainty and error is due to additional precipitation falling between the forecast issue date (e.g., January 1st) and the end of the target season (e.g., September). Seasonal climate information and forecasts offer the potential to improve the skill and lead time of water supply forecasts by reducing the uncertainty about future precipitation. This paper reviews the use of climate information in operational water supply forecasts at the Natural Resources Conservation Service's National Water and Climate Center and elsewhere. It also identifies the benefit gained from using climate information in water supply outlooks as well as the potential hazards arising from climate forecast use and abuse.