Groundwater Connection between Glaciers and Streams under a warming Climate

The role of melting glaciers in groundwater replenishment and consequent groundwater discharge to streams is often overlooked. Glacier meltwater seeps into soils and emerges back into downslope streams. These processes could play a critical role in sustaining streamflow when groundwater is the main source of water for the streams. Under warming in watersheds with glaciers, groundwater can be an increasingly important contributor to streamflow. Better understanding of seasonal and long-term variations in streamflow will improve predictions of how melting glaciers impact downstream hydrology and ecosystems and inform water management. This project examines the groundwater connection between melting glaciers and mountain streams. The overarching question is: What is the role of groundwater in connecting melting glaciers to streamflow in mountain watersheds? This study has direct implications for water resource management in a changing climate. This project is a collaboration between University of Colorado Boulder and Salish Kootenai College, which has 75% Native American students. Through planned research and mentoring activities, this project will provide opportunities for education and professional development of students from a diverse background and for outreach to Native American communities. Streamflow in glacierized watersheds has increased in recent decades during late summer to winter when surface runoff to streams is minimal. It is hypothesized that melting glaciers enhanced recharge to groundwater, aquifers are more permeable because of thawing frozen ground, and consequently groundwater discharge to streams increases. In the long run, such groundwater discharge to streams cannot be sustained as melting glaciers may disappear. Three specific research questions are: (1) How does glacier meltwater correlate to streamflow temporally and spatially? (2) How does a changing climate affect aquifer permeability as aquifers undergo seasonal freezing and thawing and long-term degradation of frozen ground? (3) How do changes in groundwater and streams affected by glacial meltwater influence downstream ecosystems? To address these questions, the project has three main tasks: (1) Characterize two representative watersheds with glaciers in Colorado and Montana that share commonalities but are distinct in scales and hydrologic conditions; (2) Analyze relevant data focusing on air temperature, glacier melt, streamflow, groundwater levels, and water temperature; (3) Synthesize the data and conduct numerical modeling that couples heat transfer and water flow. These tasks will be carried out in both field and laboratory settings. 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.