The hydrogeology of Moab-Spanish Valley, Grand and San Juan Counties, Utah, with emphasis on maps for water-resource management and land-use planning (SS-120)

By: M. Lowe, J. Wallace, S. M. Kirby, and C. E. Bishop

Contains a 40-page report with an 83-page appendix and 12 maps that address ground-water conditions in Moab-Spanish Valley’s valley-fill aquifer and provide recommendations for water-resource management and land-use planning. The maps are described in detail in the report and show geology; Glen Canyon Group depth, thickness, ground-water compartments, and fractured characteristics; valley-fill thickness; recharge and discharge areas; total-dissolved-solids concentration; nitrate concentration; ground-water quality class; potential contaminant sources; and recommended lot size.

Moab and Spanish Valleys are two contiguous valleys in southeastern Utah, herein referred to as Moab-Spanish Valley. Moab-Spanish Valley is a semirural area in Grand and San Juan Counties that is experiencing an increase in residential development. While most of the development in the Grand County portion of Moab-Spanish Valley is on a community sewer system, development in the San Juan County portion uses septic tank soil-absorption systems for wastewater disposal. Many of these septic-tank systems are on valley-fill deposits that are a drinking-water aquifer for the area. The purpose of our study is to provide tools for water resource management and land-use planning; to accomplish this purpose we (1) characterize the relationship of geology to ground-water conditions in the Glen Canyon and the unconsolidated valley-fill aquifers, (2) classify the groundwater quality of the Glen Canyon (east of the valley only) and valley-fill aquifers to formally identify and document the beneficial use of ground-water resources, and (3) apply a ground-water flow model using a mass balance approach to determine the potential impact of projected increased numbers of septic-tank systems on water quality in the valley-fill aquifer and thereby recommend appropriate septic-system density requirements to limit water-quality degradation.

Other Information:
Published: 2007
Pages: 40 p. + 83 p. appendix
Plates: 12 pl.
Scale: 1:50,000 and 1:100,000
Location: Grand and San Juan Counties