Using geochemical data to identify sources of salinity to the freshwater Navajo aquifer in southeastern Utah

Ground water is an important freshwater source for domestic and livestock uses in southeastern Utah because of the arid climate and unavailability of surface water from the San Juan River. The study area includes about 1,200 square miles in the southeastern corner of Utah (fig. 1). Precipitation on mountainous areas north, south, and east of the study area (fig. 2) seeps into the Navajo and overlying aquifers where the sandstones that contain the aquifers are exposed at the surface along mountain flanks. The ground water then moves slowly away from the mountainous areas toward the area of lowest elevation 109°30' in the region, the San Juan River. The ground water reappears at land surface where it discharges as seepage to the San Juan River or is consumed by vegetation on the flood plain. Generally, wells finished in the Navajo aquifer near the San Juan River do not require pumping because water flows freely from the well casing when it is not sealed.