Insights into Recharge Processes in Mountain-Block Hydrology Using Isotopic and Geochemical Characterization
Date
2021-09
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Abstract
Mountain block hydrology, including mountain streamflow generation and aquifer recharge in both mountains and prairies, depends on the infiltration and transport of mountain precipitation. Yet these recharge processes are not yet fully understood, and the two dominant paradigms regarding mountain recharge appear to be in conflict – Mountain Block Recharge (MBR) suggests adjacent prairie aquifers are recharged by deep flowpaths from mountain blocks, while alpine recharge suggests local flowpaths generate most mountain streams, which then recharge prairie aquifers at the mountain front. This thesis investigates this apparent dichotomy by analysing mountain recharge, aquifer storage, and streamflow generation using water geochemistry and isotopes in the upper (unreqgulated) reach of the Elbow River, an eastern slopes watershed. Water isotopes in precipitation and streamflow demonstrate that the young water fraction (Fyw) methodology is not well suited to areas with overwinter snowpack, but that average water isotope composition of winter baseflow shows ~20% of streamflow is derived from the previous year’s precipitation, suggesting rapid infiltration and throughflow. Silica and sulfate in streamflow and groundwater samples, along with sulfate isotopes, show that siliciclastic and carbonate aquifers contribute water equally to the Elbow River despite greater carbonate volume in the watershed, and that aquifer residence times are less than 10 years. Finally, analyzing the same geochemical components in late October baseflow along the length of the Little Elbow shows that high, cold precipitation infiltrates and is transported along intermediate and deep flowpaths before becoming streamflow at low elevations. Together, these findings suggest that the dominant paradigms are really two aspects of the highly dynamic and interconnected nature of mountain block hydrology.
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Keywords
MBR, Mountain Block Hydrology, Isotopes, Sulfate, Silica, Young Water, Elbow River, isotope geochemistry, water geochemistry
Citation
Campbell, É. (2021). Insights into recharge processes in mountain-block hydrology using isotopic and geochemical characterization (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.