USE OF GROUNDWATER DATING AND NOBLE GAS THERMOMETRY AND BAROMETRY TECHNIQUES TO QUANTIFY GROUNDWATER INPUT TO MATHESON WETLAND PRESERVE IN MOAB, UTAH

The Matheson Wetland Preserve (MWP), an 875-acre bottomland in Moab, Utah, is the last intact wetland along the Colorado River in Utah and home to about 175 species of birds throughout the year. The hydrology of the MWP is dominated by discharge of various regional springs, irrigation runoff, and river flooding events occurring every five to ten years. The MWP is at the distal end of the Glen Canyon Group Aquifer system, suggesting that the wetlands are vulnerable to development in nearby Moab, Utah. Groundwater dating and noble gas thermometry and barometry techniques are being used to evaluate the origin, residence time, and flux of groundwater in the system. Preliminary tritium and noble gas studies show that the springs feeding Moab city are related to the Glenn Canyon Group Aquifer, older untritiated water recharged in the La Sal Mountains at an elevation of about 2000 m. Although the MWP is down gradient from the Moab city springs, groundwater within the MWP is much younger, suggesting another more local source. The results of tritium/helium-3 dating, and noble gas concentrations (including helium-4) from multilevel monitoring wells and piezometers located along hydrologic cross sections will be presented.