Comparison and Development of Season-ahead Hydrologic Forecasts for the Upper Colorado River Basin

Since 1980, the U.S. has experienced 26 billion-dollar drought events that in aggregate have caused an estimated $250 billion in damages. These economic impacts are severe and widespread, impacting farmers reliant on water supply for irrigation, urban communities in arid climates, and ecosystems threatened by anthropogenic water consumption. Season-ahead streamflow forecasts are one tool for addressing drought-driven damages when coupled with infrastructure management of storage reservoirs, prompting drought management actions at lead times of months to seasons or longer. Such forecasts can also provide impetus to shift water use toward high priority sectors and activities. Enhanced management practices are desperately needed in the drought-prone western U.S., including the Colorado River Basin (CRB), where decreased snowpack due to climate change and rapid urban growth is intensifying water scarcity risks. Numerous forecast products exist for the CRB; we compare model performance for a number of these forecast products at various lead times. Further, we present a new forecast model framework for the CRB that explicitly captures asymmetric relationships between climate indices and hydrologic variables. Future research will focus on coupling seasonal forecasts with large-scale CRB water allocation models to explore management strategies and economic impacts related to long-term drought conditions.