Holocene sediments at Emerald Lake in central Utah (3090 m a.s.l), document the paleohydroclimatic history of the western Upper Colorado River headwater region. Multi-proxy analyses of sediment composition, mineralogy, and stable isotopes of carbonate (d18O and d13C) show changes in effective moisture for the past ca. 10,000 years at millennial to decadal timescales. Emerald Lake originated as a shallow closed-basin cirque pond during the early Holocene. By ca. 7000 cal yr BP, higher lake levels and carbonate d18O values indicate rising effective moisture and higher proportions of summer precipitation continued at least until ca. 5500 cal yr BP when a landslide entered the lake margin. Between ca. 4500 and 2400 cal yr BP dry conditions at Emerald Lake envelop the timing of the 'Late Holocene Dry Period' identified at lower elevations. For the past ca. 2500 years, Emerald Lake d18O values were relatively low, indicating wetter conditions and higher snow input (compared to rain) except for dry periods at ca. 2000 cal yr BP and during the Medieval Climate Anomaly at ca. 1000 and ca. 500 cal yr BP. Results provide a long-term perspective on precipitation extremes that influence regional water supplies from a snow-dominated catchment typical of the predominant source region for the Upper Colorado River.