Delving deep into mountains for future water security

Covering around a quarter of the Earth’s land surface, mountains supply water to billions of people and underpin global water, energy and food security. Mountainous regions receive disproportionately high rainfall, which feeds the rivers flowing to lower-lying areas where water demand is often greatest. Crucially, mountains also regulate this supply, storing water during wetter periods and releasing it during dry spells, which is why they are sometimes referred to as the ‘natural water towers’ of the world.

However, exactly where this water is stored and how it is released remains only partially understood. Much of the existing research has focused on the visible parts of mountain water systems including rivers, lakes, snow and glaciers. While these are undoubtedly important, we could be missing a vast, largely invisible component: the water stored deep within the mountain bedrock.

Emerging research is beginning to challenge the conventional understanding of mountain water systems. Studies using environmental tracers, which are chemical and biological ‘fingerprints’ that reveal where water has travelled, and geophysical imaging techniques that allow scientists to ‘see’ beneath the surface, suggest that significant volumes of water may move through deep mountain groundwater systems. These systems could be more resilient to climate change, potentially sustaining river flows and supporting downstream communities in an increasingly variable climate.

Taiwan’s steep, rainfall-rich mountain landscapes provide an ideal natural setting for studying how water moves through complex hydrogeological systems. A new project, led by BGS in collaboration with the UK Centre for Ecology & Hydrology (UKCEH), New Mexico Tech, the University of Basel and National Cheng Kung University, will investigate how water flows through these systems, focusing on a mountain-fed river basin in central Taiwan.

By combining environmental tracers with advanced geophysical techniques, we can begin to map how water moves through mountain bedrock in ways that haven’t been possible before. These approaches give us powerful new insight into subsurface processes that are largely invisible, but potentially vital for long-term water resilience.

Prof Mark Person, co-investigator, New Mexico Tech.

The project also benefits from a unique groundwater observation network in the region. By tracking how water travels through the mountain bedrock, the team aims to build a first-of-its-kind, data-informed digital model of mountain groundwater flow.

Mountains are sometimes described as the world’s water towers, but we still don’t fully understand how they store and release water, especially beneath the surface. This project aims to uncover the hidden role of groundwater within mountain systems, which could be critical for sustaining water supplies as climate variability increases.

Dr Jon Mackay, BGS principal investigator

This research has the potential to establish a new paradigm for mountain hydrology by integrating the role of deep groundwater into our understanding of how mountain water systems function. In doing so, it will help develop more robust tools to support water resource management and climate change adaptation strategies in mountain-fed river systems around the world.