Multi-Tracer Assessment of Recharge Sources and Flowpaths In an Arid Landscape

Abstract:

In an effort to better understand the resilience of groundwater on the South Rim of the Grand Canyon to contamination and depletion, environmental and isotopic tracer data was compiled and collected from springs and wells. Findings from the study support a revised conceptual model which identifies structural features as a major control on groundwater chemistry and identifies previously unrecognized recharge sources. Stable isotope end-member and noble gas solubility models indicate recharge is largely from winter precipitation but also from summer monsoonal runoff. Helium isotope analysis indicates a limited connection between shallow meteoric and deeper flow systems. Interpretation of age tracers (tritium, carbon-14) showed a wide range of groundwater ages which supports both local and regional flowpaths and recharge sources. The multi-tracer approach used here revealed additional complexity in a previously well studied groundwater flow system.