Groundwater Connection between Glaciers and Streams under a warming Climate

冰川融化在补充地下水和随后向溪流排放地下水方面的作用常常被忽视。冰川融水渗入土壤，再流回下坡的溪流。当地下水是河流的主要水源时，这些过程可能在维持河流流动方面发挥关键作用。在有冰川的流域变暖的情况下，地下水对河流流量的贡献越来越重要。更好地了解河流流量的季节性和长期变化将改善对冰川融化如何影响下游水文和生态系统的预测，并为水管理提供信息。这个项目考察了融化的冰川和山间溪流之间的地下水联系。首要的问题是：地下水在连接融化的冰川和山区流域的河流方面发挥了什么作用？这项研究对气候变化下的水资源管理具有直接意义。这个项目是科罗拉多大学博尔德分校和萨利什库特奈学院的合作项目，该学院有75%的印第安学生。通过有计划的研究和指导活动，该项目将为来自不同背景的学生提供教育和专业发展的机会，并为美洲原住民社区提供服务。近几十年来，在夏末至冬季期间，冰川流域的河流流量有所增加，此时地表径流最少。据推测，冰川融化增加了地下水的补给，由于冻土融化，含水层的渗透性更强，因此向溪流排放的地下水增加。从长远来看，由于冰川融化可能会消失，这种向河流排放地下水的做法是无法持续的。三个具体的研究问题是：(1)冰川融水与河流在时间和空间上是如何关联的？(2)当含水层经历季节性冻融和冻土长期退化时，气候变化如何影响含水层的渗透性？(3)受冰川融水影响的地下水和河流的变化如何影响下游生态系统？为了解决这些问题，该项目有三个主要任务：(1)描述科罗拉多州和蒙大拿州两个具有代表性的流域的冰川特征，这两个流域具有共性，但在规模和水文条件上有所不同；(2)分析气温、冰川融化、河流流量、地下水位、水温等相关数据；(3)综合数据，进行传热与水流耦合的数值模拟。这些任务将在现场和实验室环境中进行。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.