243 Hydrogeology (Posters) II

ASSESSMENT OF SOURCES OF SALINITY FROM SHEEP CREEK TO THE PARIA RIVER, SOUTHERN UTAH

Paper number: 243-20
Program: Technical Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

The Paria River in Grand Staircase Escalante National Monument, UT (GSENM) exceeds EPA limits of salinity, chloride and total dissolved solids. Sheep Creek is an ephemeral stream and a major western tributary to the Paria River, draining the eastern side of Bryce Canyon National Park (BCNP). This study examines springs (ground water) and surface water collected in the fall and spring seasons. Samples sites originate at the headwaters of Sheep Creek in BCNP and extend down through quaternary alluvium to the Paria River in GSENM. Five groups of samples were collected for a baseline characterization of water quality in Sheep Creek. Major cation and anion analyses were used to examine geochemical trends and water quality. Sample groups were chosen based on springs emerging from various geologic formations. The headwaters of Sheep Creek issue from the Claron Fmn (Swamp Sites), the next site emerges from the Straight Cliffs Fmn (Daves Sites), a spring flows from the Entrada Fmn (Erez Sites), while another emerges from the Carmel-Page Sandstone, the confluence of Sheep Creek and the Paria River flow through Navajo Sandstone.

Preliminary results reveal a trend of increasing ionic strengths in Sheep Creek as water flows downstream. All constituents spike at Sheep Creek except bicarbonate which peaks at the Straight Cliffs Fmn site. During both seasons ground water in Sheep Creek has higher constituent values than surface water. The geologic tongues and pockets between the Entrada Fmn (Erez Sites) and the Carmel Page Sandstone (Sheep Sites) contain beds of gypsum. This may account for the highest values of sulfate being in the water sampled below these beds, the Sheep Creek sites. Further downstream at the confluence of Sheep Creek and the Paria River sulfate levels drop to significantly lower values. The Glen Canyon aquifer in the Navajo Sandstone feed the Paria River and may account for this reduction in sulfate levels.

The state of Utah needs information to address water quality in the Paria River. This study will provide baseline data to GSENM about the main tributary draining BCNP and the western section of GSENM. Water is a limited and valuable resource in GSENM. This data will assist Monument managers in monitoring the seasonal variability of water quality in Sheep Creek and the Paria River for the unique wildlife and vegetation in the area.