HYDROLOGIC AND HYDROGEOLOGIC ASSESSMENT OF THE SURFACE WATER AND GROUNDWATER RESOURCES AFFECTING THE CITY OF MOAB SPRINGS AND WELLS, MOAB, UTAH: THE ROLE OF FRACTURE AND FAULT ZONES IN DETERMINING GROUNDWATER FLOWPATHS, STORAGE CAPACITY, RECHARGE, AND WATER BALANCES IN MOUNTAIN/PLATEAU HYDROLOGIC SYSTEMS

The purpose of this study is to perform a Hydrologic and Environmental System Analysis (HESA) of the City of Moab, Utah Springs and Wells area, supported by GIS databases and maps, to develop an updated Conceptual Model of hydrogeologic and hydrologic characteristics of the groundwater and surface water systems; develop a series of water budgets, predevelopment and current, to be used for water rights defense, and urbanization- and climate-change driven planning affecting the groundwater sustainability of the region; update the delineations of the drinking water source protection (DWSP) zones for Moab’s wells and springs; and develop a comprehensive monitoring plan to further characterize the complex La Sal Mountain/Spanish Valley hydrologic systems in response to anticipated future perturbations due to climate and human activity.

The results of this study are a new conceptual model on how mountain/plateau hydrologic systems are structured and function with respect to subregional and local fracture and fault zones acting as French drains, as opposed to matrix flow, that dominate the surface water and groundwater flowpaths, storage capacity, and recharge, and ultimately account for the sustainability of these complex hydrologic systems; how water balances guided by this conceptualization more accurately represent the properties of the complex hydrologic systems for water rights, management, and modeling purposes, and improve delineations of drinking water source protection zones and development of water monitoring plans. Specific hydrogeological results include: 1) the characterization of the Glen Canyon aquifer and Mill Creek gorge in terms of connectivity, fracture flow and French drains that control the recharge, storage, and discharge of groundwater in the main bedrock system affecting Moab’s springs and wells, and 2) the delineation of 5 separate groundwater systems connected mostly by surface water links that compose the La Sal Mountain-Spanish Valley regional system. The water balance analyses revealed that direct local recharge from precipitation exceeded 50% of total recharge indicating that climate change resulting from declining precipitation may be more important than reduction of mountain snowpack for determining groundwater sustainability in some desert systems.