Ground water - surface water interactions in the lower Virgin River area, Arizona and Nevada

Lynn Metcalf, University of Nevada, Las Vegas


This study assessed interactions between ground water and surface water in the lower Virgin River, Arizona and Nevada, using stable isotopes and major ions as environmental tracers. The study reach starts at the Virgin River Gorge in Arizona and terminates at Lake Mead in Nevada, 80 km downstream. Discharge data showed that major sources of water for the lower Virgin River were discharge from the upper Virgin River and the Littlefield Springs, with minor amounts from Beaver Dam Wash, a perennial tributary. No strong evidence was found for ground-water seepage into the channel. In general, dissolved solids concentrations increased downstream because of water loss due to evapotranspiration. From the environmental tracer results, three general water types were identified: (1) local water including springs and streams in surrounding mountains, surface water from Beaver Dam Wash, and ground water from the Beaver Dam Wash floodplain aquifer; (2) Virgin River water consisting of surface water from the Virgin River, ground water from the Virgin River floodplain, and flow from the Littlefield springs; and (3) ground water from deep aquifers underlying the floodplain aquifers. The local water is the most isotopically enriched ({dollar}\delta{dollar}D values between {dollar}-{dollar}91 and {dollar}-70\perthous{dollar}) and has the lowest dissolved solids concentrations of all the waters sampled. Deep ground water is the most isotopically depleted of the waters with {dollar}\delta{dollar}D values ranging from {dollar}-{dollar}106 to {dollar}-99\perthous{dollar}. Virgin River water is isotopically intermediate ({dollar}\delta{dollar}D from {dollar}-{dollar}97 to {dollar}-87\perthous{dollar}) but has the highest dissolved solids of all waters sampled.