EVIDENCE FOR A SUB-REGIONAL HYDRAULIC BARRIER IN SOUTHEASTERN NEVADA

A synthesis of monitoring records from southeastern Nevada, near the terminus of the White River Flow System (that involves a series of hydrographic basins and interbasin flow through carbonate-rock terrain), has improved our understanding of groundwater flow-system configuration in an area immediately north of Las Vegas. Two flow domains, with internally consistent physical properties and dynamic responses to seasonal pumping, have been identified. This barrier to flow subdivides the Arrow Canyon Range Cell of the Regional Carbonate Aquifer into “northern” and “southern” flow fields. Very small hydraulic gradients and large transmissivities characterize the Arrow Canyon Range Cell.

There are important water-management implications associated with this particular flow barrier. The Muddy River, tributary to the Colorado River, is sustained by discharge from a group of large springs that issue from the Carbonate Aquifer near Moapa. Ambitious proposals to tap groundwater resources northwest of the Muddy River springs in Coyote Spring Valley have attracted considerable investment, based on the assumption that springflows and hence Muddy River flows would not be impacted by the proposed developments. The flow barrier rules out any contribution to these developments, or to the Muddy River springs, by waters of the “southern” flow field; this resource is largely unexploited. Extractions from the “northern” flow field, which extends northwestward from the Muddy River springs and includes Coyote Spring Valley, will impact Muddy River flows on essentially a one-to-one basis. Any such impact is untenable under Nevada water law.