GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 91-13
Presentation Time: 11:30 AM


WALLACE, Janae, UGS, box 146100, salt lake city, UT 84114; Utah Geological Survey, Salt Lake City, UT 84114 and SCHLOSSNAGLE, Trevor, UGS, box 146100, Box 146100, salt lake city, UT 84114; Utah Geological Survey, Box 146100, Salt Lake City, UT 84114

Bryce Canyon City occupies part of southwestern Johns Valley in central Utah, adjacent to Bryce Canyon National Park. Due to potential increase in development, we are investigating the area to characterize the hydrogeology of the southwestern Johns Valley drainage basin as it pertains to the occurrence and flow of groundwater, with emphasis on characterizing groundwater quality, flow paths, and connection to surface water, principally the East Fork of the Sevier River.

Water quality and the potential for water-quality degradation are critical elements determining the extent and nature of future development in the basin. Most development is on unconsolidated basin-fill deposits, the primary source of groundwater. The community of Bryce Canyon City is an area of active tourism and, therefore, potential increase in growth (likely from hotel development). Increased demand on drinking water would warrant careful land-use planning and resource management to preserve Johns Valley’s surface and groundwater resources. We measured water levels and sampled water during autumn 2018 and spring 2019 in selected wells, springs, and streams. Preliminary data show overall good water quality and fluctuating water levels in wells. Wells completed in alluvium generally recorded water level rise during spring 2019; water levels have dropped or remain similar to autumn measurements in bedrock wells.

We analyzed samples from 30 sites for major-solute chemistry and environmental isotopes and tracers, including total dissolved solids (TDS), nitrate, and dissolved metals. Data from autumn 2018 indicate excellent water quality, with TDS concentrations ranging from 192 to 716 mg/L, with an average of 304 mg/L. Chemistry and stable isotope results from samples taken in autumn 2018 and spring 2019 are pending as well as radiogenic isotopes (tritium and carbon-14). Possible changes in chemistry in water from alluvial wells may occur due to record-breaking winter precipitation in the valley and surrounding plateaus.