Western U.S. water managers facing changing climate and growing populations are seeking new tools to guide their planning and operational decision making. This presentation highlights two key tools that emerged from a five-year collaboration between university researchers and Salt Lake City Department of Public Utilities. Using a 100-year record of streamflow from ten watersheds, we found that variability in groundwater storage, derived from winter streamflow, is the primary factor controlling runoff efficiency. Long-term records of precipitation, snowmelt dynamics, and groundwater storage were used to construct a linear model that calculates annual streamflow volume with an error of 5%. Through further investigation of climate factors affecting groundwater storage, we found a significant relationship between Atlantic Ocean temperatures (Atlantic Quadpole Mode, or AQM), Pacific Ocean temperatures (El Niño Southern Oscillation or ENSO), and winter precipitation in the western U.S. The connection between the AQM, ENSO, and western U.S. hydroclimate is observed in the historical precipitation record and a 10,000-year global climate model simulation with perpetually fixed modern greenhouse gas concentrations. The relationship between winter precipitation, AQM, and ENSO is particularly useful in the prediction of winter precipitation in locations like northern Utah where ENSO has no statistical relationship with winter precipitation. This research was used to develop a new climate tool that provides a forecast of December – March precipitation for the western U.S.
