The impact of precipitation phase and aquifer type on changing groundwater levels in mountain regions of Canada and the United States

Abstract

Groundwater in alpine regions plays an essential role in downstream water supply. As the climate warms, mountain water resources are under threat with reduced snowpack, glacier recession, and precipitation phase change that can negatively impact summer streamflow. However, the extent to which such global changes can impact the mechanisms that contribute to groundwater recharge remains poorly understood. This project aims to address the limited spatial and temporal extents of observational studies and enhance our understanding of long-term trends across various geographical boundaries of groundwater in mountainous regions. We analysed a dataset of 171 observation wells from mountain regions across Canada and the US, categorizing wells as snow-dominated, rain-dominated, and high-temperature rain-dominated hydrological regimes based on temperature thresholds. Additionally, we considered three aquifer types (confined, unconfined, and mixed) and the well depth as the potential explanatory variables. We conducted Kruskal- Wallis and Spearman correlation analysis on the above against the groundwater level trends, respectively. Our results indicated a non-significant difference (p = 0.1687) between the three hydrological regimes, a statistically significant difference (p = 0.0182 < 0.05) in the trends observed between the three-aquifer type, and lastly a weak negative Spearman correlation of ρ = -0.01089 between trend and well depth, which is not statistically significant (p<0.05). This study emphasizes the value of extending research on mountain groundwater to a larger spatial extent and offers significant insights into how various factors can influence groundwater recharge in mountains.