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 c...