Identification and Modeling the Impact of Marine Shale Bedrock on Groundwater and Stream Salinity: Upper Colorado River Basin

摘要

Recent studies have shown that groundwater is a major contributor to stream salinity in the Upper Colorado River Basin. The primary salt sources are the marine shales and that underlie the soils of much of the basin. A field site in the Price River Basin, a tributary to the Green and Colorado Rivers, was selected to study the physical and chemical factors that control the interactions between groundwater and these shales. On the basis of the CH2M Hill study and the additional data collected during the study groundwater flow paths, salt transport and weathering processes were identified. Results show that the groundwater evolves from a calcium-bicarbonate water to a sodium-sulfate water with depth and distance along the flow paths. Geochemical equilibrium modeling and mass balance computations were performed using the USGS models PHREEQE and BALANCE. A preliminary saturated-unsaturated two-dimensional flow model (UNSAT) was implemented along the identified groundwater flow path.