Collaborative Research: Warming and drought in the critical headwaters of the Snake, Colorado, and Missouri rivers since the last deglaciation

University Of Wyoming, Laramie WY

Investigators

Abstract

Ongoing and future droughts threaten the water supply of the American West by reducing the flows of the three major river basins of the western United States: the Snake-Columbia, Green-Colorado, and Missouri rivers. Current supplies only meet 80% of water demand in rapidly growing states like Colorado, but reduced precipitation, shifts from snow to rain, accelerated Spring snowmelt, and increased evaporation can further amplify the long-standing challenge of Western water resource management. Geological evidence from past centuries and millennia indicate that the region can become substantially drier than today. Furthermore, the current generation of models used to forecast the water supply fail to simulate the apparent severity of past dry periods, raising the alarming possibility that they will dramatically underestimate future water supplies vital to major urban areas, agriculture and energy sectors, and iconic ecosystems. There is thus a pressing need for robust constraints on how dry the headwaters of the three major Western rivers can become. To do so, this project will study the magnitude and drivers of aridity in the Rocky Mountains over the 15,000 years since the last ice age. Public communication of the scientific findings will include coordination with Grand Teton National Park, where two of the study sites are located, and K-12 teachers and students through the Teton Science School. The project will quantify past changes in precipitation, evaporation, and other processes (snowmelt) in the mountains of Wyoming and Colorado to create robust benchmarks for evaluating changes to critical Western water supplies. To test hypotheses regarding 1) the severity and patterning of past droughts, 2) their driving factors, and 3) differences among existing lines of evidence, the work will use geological evidence from pairs of low- and high-elevation lake from across the “Triple Crown” headwaters of the Snake, Green, and Missouri rivers. The study design will evaluate past shifts in topographic and latitudinal moisture gradients across the headwater watersheds. The work will use analyses of sediment cores from the lakes to reconstruct past water levels, water temperatures, and the hydrogen and oxygen isotopic signatures of key hydrologic processes. This award is co-funded by the Division of Earth Sciences and the Division of Atmospheric and Geospace Sciences. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.