Challenge
The Moapa Valley Water District (MVWD) has served the domestic water needs of Moapa Valley since 1960. Generally located on I-15 between Mesquite and Las Vegas, Nevada, the MVWD’s services area includes Overton, Logandale, Glendale and Moapa. Approximately 167 miles of pipeline with a service territory of 75 square miles and approximately 8,000 residents rely on the water source to deliver clean potable water.
Since 2009, GZA has analyzed spring flow data in the Muddy Springs Area on behalf of the Moapa Valley Water District (MVWD) in Nevada. The annual monitoring report is submitted to the Nevada Division of Water Resources in cooperation with the U.S. Department of Interior’s National Park Service, U.S. Fish and Wildlife Service, and Nevada Power Company (NPC). The springs provide flow to sustain critical habitat for the endangered Moapa dace, and the report evaluates if groundwater extraction affects spring flow and thus critical habitat for the dace.
Solution
In conjunction with the 2012 annual report, GZA analyzed pumping effects on the spring complex caused by a 2-year, 8,000 afa pumping test in the Regional Carbonate Aquifer ordered by the Nevada State Engineer (Order 1169). GZA determined that spring discharge decreased at higher elevation springs, but the pumping had no effect on Muddy River stream flows measured at the Muddy River gage. The analyses helped establish mitigation trigger levels that would require reductions in pumping if spring or stream flows dropped below minimum target levels. Since the trigger levels were established GZA has been evaluating stream flows and MVWD pumping and advising the District on compliance issues related to pumping, river depletions, and endangered species. GZA utilized data collected during continued monitoring of spring and stream flows after the end of the Order 1169 pumping test, in combination with records of pumping within the contributing groundwater basins, to estimate sustainable yield of the basins and provide the Nevada State Engineer with recommendations for administration of water rights within the Order 1169 basins, and provided expert testimony on groundwater-surface water interaction in a two-week Nevada State Engineer administrative hearing.
Benefit
GZA’s ability to analyze and synthesize the interaction between ground and surface water (spring discharge and river flow) helps to ensure the protection of endangered species. It further represents an analysis relating to the properties, distribution, and circulation of water on the land surface and underlying rock as well as studies or activities necessary or desirable to facilitate improved understanding and management of surface water systems of the State. This project also provides an example of GGI’s experience with evaluating and advising clients on technical, institutional, and environmental compliance issues.
