Summary of ground-water sampling in the Courthouse Wash Area, Grand County, Utah

Kirby, Stefan

This report presents data from ground-water sampling of springs and wells in the Courthouse Wash area. A total of eight sites, including four wells and four springs, were sampled in March of 2006. All samples were analyzed for 1) general solute chemistry including major anions and cations, nitrite and nitrate, total and dissolved phosphate, 2) stable isotopes of deuterium and oxygen, 3) tritium, and 4) carbon isotopes. Results indicate that the three springs that issue near the base of the Moab Member of the Curtis Formation, including Sevenmile Canyon Boundary Spring, Poison Ivy Spring, and Sleepy Hollow Spring, consist of ground water recharged approximately since or just prior to 1950. These three springs also have a distinct solute composition, different from that of all other sampling sites. Based on the data presented these three springs do not likely receive any ground water from beyond the recharge areas delineated by Hurlow and Bishop (2003). By contrast, Courthouse Wash Boundary Spring likely contains a mixture of old ground water recharged at least several thousand years ago and premodern ground water recharged just prior to 1950. The presence of old water requires that flow paths are long and or recharge rates are low for this spring. This implies the potential for interference from future ground-water development in the Slick Rock and Moab Member aquifer upgradient of the spring, beyond the recharge area delineated by Hurlow and Bishop (2003). All wells, except the Arches Headquarters well, consist of a mix of old ground water (recharged between several thousand and ten thousand years ago) and modern ground water (recharged since 1950). Ground water sampled at the Arches Headquarters Well consists of modern water recharged since 1950.

Summary of ground-water sampling in the Courthouse Wash Area, Grand County, Utah

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