Using noble gas tracers to constrain a groundwater flow model with recharge elevations: A novel approach for mountainous terrain

Water Resources Research
By: , and 

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Abstract

Environmental tracers provide information on groundwater age, recharge conditions, and flow processes which can be helpful for evaluating groundwater sustainability and vulnerability. Dissolved noble gas data have proven particularly useful in mountainous terrain because they can be used to determine recharge elevation. However, tracer-derived recharge elevations have not been utilized as calibration targets for numerical groundwater flow models. Herein, we constrain and calibrate a regional groundwater flow model with noble-gas-derived recharge elevations for the first time. Tritium and noble gas tracer results improved the site conceptual model by identifying a previously uncertain contribution of mountain block recharge from the Coast Mountains to an alluvial coastal aquifer in humid southwestern British Columbia. The revised conceptual model was integrated into a three-dimensional numerical groundwater flow model and calibrated to hydraulic head data in addition to recharge elevations estimated from noble gas recharge temperatures. Recharge elevations proved to be imperative for constraining hydraulic conductivity, recharge location, and bedrock geometry, and thus minimizing model nonuniqueness. Results indicate that 45% of recharge to the aquifer is mountain block recharge. A similar match between measured and modeled heads was achieved in a second numerical model that excludes the mountain block (no mountain block recharge), demonstrating that hydraulic head data alone are incapable of quantifying mountain block recharge. This result has significant implications for understanding and managing source water protection in recharge areas, potential effects of climate change, the overall water budget, and ultimately ensuring groundwater sustainability.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Using noble gas tracers to constrain a groundwater flow model with recharge elevations: A novel approach for mountainous terrain
Series title Water Resources Research
DOI 10.1002/2015WR017274
Volume 51
Issue 10
Year Published 2015
Language English
Publisher American Geophysical Union
Contributing office(s) Central Mineral and Environmental Resources Science Center
Description 20 p.
First page 8094
Last page 8113
Online Only (Y/N) N
Additional Online Files (Y/N) N