The role of groundwater in mountain hydrological systems under a changing climate

Climate change is progressing rapidly at high elevations such that mountain snowpack and glaciers are shrinking globally, snowmelt is occurring earlier in the year and evapotranspiration (ET) is increasing, threatening globally important mountain runoff and water resources. Groundwater has recently been recognized as a critically important part of mountain hydrological systems and it is expected to help sustain mountain streamflow as snow and ice storage declines. However, groundwater is not immune to the impacts of climate change; changing air temperatures, snow/rain fraction and vegetation patterns may negatively impact mountain groundwater storage. Our ability to design effective water resource management strategies for mountain regions is limited by exceptionally scarce observational data of groundwater, hydrogeologic complexity and uncertainty around how mountain groundwater systems are changing. The overall goal of this research program is to improve understanding of linked groundwater and surface water processes in mountain regions globally and project future changes to inform water resource management. Two medium-term objectives will be tackled over the next five years. First, unconventional data sources (e.g., groundwater springs, wetland wells) will be developed and incorporated into field monitoring and numerical modeling to overcome data limitations and improve observational capacity of mountain groundwater systems. New integrated observational and modelling approaches will be tested at a local, relatively accessible field site in the Cape Breton Highlands National Park, Nova Scotia, to investigate groundwater recharge sources and variability. Second, a global dataset of mountain groundwater field data will be compiled, incorporating observation wells, groundwater springs and wetland wells. This data will be statistically analysed for trends and combined with existing global datasets to identify key vulnerability factors (e.g., topography, geology, climate). Based on the new global dataset, three-dimensional groundwater flow numerical models will be developed, and climate projections will be applied to elucidate future mountain groundwater storage loss and the consequences for water resource management. 8 Highly Qualified Personnel (2 PhD, 2 Master's and 4 Undergraduate students) will be trained as part of this research. This research program will expand our ability to measure, model and manage mountain groundwater, a hidden, understudied, yet critical water resource. It constitutes the first effort to assess large-scale changes in mountain groundwater systems across different geographic settings to reveal emerging trends and project future impacts. This work will inform the design of climate change adaptation strategies and contribute to improved water management for drinking water, agriculture, hydropower and industrial use for the 1.9 billion people in the world who live downstream of mountains.