Extent of Salt Dissolution and Brine Flushing to the Dolores River in the Paradox Valley, Colorado

Ambria P. Dell'Oro, Jihyun Kim, Jennifer McIntosh

Department of Hydrology and Atmospheric Sciences

The University of Arizona, Tucson, Arizona

The Dolores River in Colorado is a tributary to the Colorado River and is widely known for its high salinity content, particularly in the Paradox Valley where the salt-containing Paradox Formation comes close to the surface. Previous research has identified dissolution of halite and gypsum as the main contributor to salinity in the shallow aquifers and Dolores River. This study aims to determine the contribution of deeper fluids such as, connate brines, associated with the Paradox Formation into shallow aquifers and the river.  In addition, we aim to constrain the extent of halite and gypsum dissolution and removal of salt over geologic time; and circulation patterns and rates of solute transport associated with the salt diapir. Water samples will be collected from brine pumping wells maintained by the Bureau of Reclamation, natural springs, and the Dolores River in the Paradox Valley.  Samples will be analyzed for their salinity content, solute and isotope chemistry and age tracers (4He, 81Kr, 14C).  Results are expected to increase understanding of fluid and solute transport associated with salt diapirism, and salinity loading to the Dolores and Colorado rivers.