NERC-NSFGEO Delving deep into the mountain block for future water security

Mountains, often called the “water towers” of the world, provide critical water supplies to billions of people by capturing precipitation and channelling it downstream. They regulate water availability, buffering lowland communities against water shortages. However, the buffering capacity of mountains is predicted to change as the climate warms, putting downstream populations at increased risk of water scarcity. Understanding these changes is key to developing effective adaptation strategies for mountain-fed communities. The primary focus of hydrologic research has been on understanding how changes in rainfall-runoff and melt from snow and glaciers will affect water supply in the future. While critically important, this research ignores groundwater flows through the mountain block, assuming that the mountain bedrock is impermeable. Recent research challenges this assumption, suggesting that significant water flows occur within deep mountain groundwater systems which may form a crucial component of current and future water mountain water cycling, providing resilience to water shortages, but their magnitude, pathways, and timescales remain largely unknown due to observational challenges. This blind spot in our understanding, undermines our capacity to develop robust impact assessments and adaptation pathways for vulnerable downstream communities. This project seeks to address this knowledge gap by exploring how groundwater in the mountain block contributes to downstream water supply. The research focuses on the Zhuoshui-Wuxi Catchment (ZWC) in central Taiwan which serves as an excellent case study due to its rich hydrogeological dataset, including borehole networks, geophysical surveys, and records of groundwater dynamics. Insights gained here will be applicable to other mountain regions such as the Himalayas, Andes, and Rockies. The project aims to answer the following research questions: RQ1) Which pathways does water take through the mountain block to the lowlands? RQ2) How long does it take for water to transit deep groundwater flow pathways? RQ3) How much do MBR and MFR fluxes contribute to the water budget of lowland areas? RQ4) Can mountain groundwater buffer future downstream water supply deficits? To achieve this the project will employ innovative methods including: Environmental Tracers: Emerging techniques, including environmental DNA and noble gases, will map deep groundwater flows and identify connections between mountain and lowland systems. Magnetotellurics (MT): This geophysical method will provide images of groundwater flow at depths of up to 10 km, offering unprecedented insights into deep subsurface flows. Numerical Models: Data from the field will be integrated into 2D and 3D hydrological models to simulate groundwater dynamics and assess its role in buffering water supplies. This research will transform our understanding of mountain groundwater flow and its role in supplementing downstream water supplies. By challenging the traditional "runoff-centric" view of mountain hydrology, a view that is replicated across the models that underpin current climate change impact assessments, the project will establish a new paradigm that incorporates the critical contributions of groundwater, with the potential to support the development of more robust strategies for managing water resources in the face of climate change. Beyond Taiwan, the insights gained will be globally relevant, aiding adaptation efforts in mountain regions worldwide.