APPLIED HYDROGEOLOGY IN THE SCOTT AND NORMA MATHESON WETLANDS PRESERVE, MOAB, UTAH

The Scott and Norma Matheson Wetlands Preserve (the “Preserve”) is a riparian ecosystem along the Colorado River, adjacent to Moab, Utah, that provides habitat to more than 200 species of wildlife and is a popular local destination for hiking, birding, and hunting. Property managers are concerned that increased water consumption upstream could impact the Preserve’s ecology. In response, they are leasing water and considering treating effluent for application to the Preserve. These mitigations are costly and require a detailed understanding of the hydrologic system of the Preserve.

Analyses of remote sensing data collected from 1993 to 2023 indicate that surface-water extent and inundation frequency have decreased since 1993, leading to changes in vegetation communities. Colorado River floods provide water and nutrients to the Preserve at the start of the growing season, but impacts are short lived. Precipitation, spring water, and groundwater are key to the extent of surface water and groundwater levels in the Preserve.

Our water budget shows that about 1000 ac-ft of water passes through the Preserve annually. Of the hydrologic inputs, as much as 9% comes from Skakel Spring—a municipal source that could potentially be used fully by Moab— and 27% comes from other springs, some of which are already leased by the Preserve. An additional 16% comes from groundwater flow in, which could be impacted by increased groundwater pumping upgradient of the Preserve. A dye tracer test confirmed that spring water flows onto the Preserve along the east margin, a portion of which recharges groundwater. This water can be piped directly to a pond within the Preserve, which would reduce recharge, but maintain razorback sucker spawning habitat, underscoring the complexity of management decisions.