Environmental tracer investigation of groundwater conditions at the Scott M. Matheson Wetland Preserve near Moab, Utah

Dissolved gas concentrations, tritium, and stable isotopes have been used to develop a conceptual model of a complex desert-wetland groundwater flow system adjacent to the Colorado River near Moab, Utah. The Scott M. Matheson Wetland Preserve lies directly across the Colorado River from a large uranium tailings pile at the topographic low of the Moab salt-collapse valley. Extreme salinity gradients and transients in hydraulic heads make the use of Darcy's law problematic with regards to delineating groundwater flow, but a reasonably self-consistent model emerges when a suite of environmental tracer data are considered. Dissolved 4He concentrations are more than two orders of magnitude larger than atmospheric solubility as little as 2 m below the Colorado River and delineate the effective boundary between a shallow, fresh groundwater system and underlying brine. The combination of tritium, stable isotope, dissolved gas, and salinity measurements allowed for clear determinatio