Insights into mountainous groundwater movement and age distributions in fractured bedrock
a) Modeled mean ages inferred from environmental tracer observations in Thiros et al. (2023a); b) total water masses grouped by age and the fraction that infiltrates as snowmelt (remainder is rain). Image courtesy of Thiros et al., 2024.
The Science
The study used numerical models and observations to investigate groundwater flow in a mountainous hillslope. The results show that soil water near the base of the hillslope receives significant contributions (over 60%) from deeper bedrock flow paths with water ages exceeding 10 years. This connectivity between the bedrock and soil systems is present throughout the year, suggesting that old groundwater plays a crucial role in hillslope hydrology.
The Impact
The study’s findings have important implications for understanding and managing mountain watersheds. By recognizing the influence of bedrock groundwater on soil water and streamflow, stakeholders can better assess the vulnerability of these systems. This knowledge can inform strategies for sustainable water management, such as protecting groundwater recharge areas and predicting the impacts of droughts and floods.
Summary
The study’s results highlight the significance of considering bedrock groundwater flow paths in mountain watershed models. Results from the numerical model and groundwater age observations demonstrate that the bedrock groundwater system influences hillslope dynamics, including evapotranspiration and streamflow generation. The findings suggest that neglecting these flow paths could lead to inaccurate predictions of water movement and age distributions in these systems. Furthermore, the study’s results have implications for understanding the role of old groundwater in sustaining ecosystem function, such as vegetation dynamics and streamflow generation. By incorporating bedrock groundwater flow paths into mountain watershed models, researchers can improve their ability to predict and manage headwater resources.
Contact
Eoin L. Brodie, Watershed Function SFA LRM
Lawrence Berkeley National Laboratory
Publications
Thiros, N. et al, Old-Aged groundwater contributes to mountain hillslope hydrologic dynamics, Journal of Hydrology, 635, (2024), DOI: 10.1016/j.jhydrol.2024.131193