John A. Korver Fluid flow from nuclear chimneys Water Resources Research 2 No. 2 Second Quarter 1966 297 310

Abstract

Artificially recharging the Las Vegas Valley groundwater system is one water resource management option available to the Las Vegas Valley Water District (District) to help meet increasing summer peak water demands. In a few years the existing water transmission system from Lake Mead will be unable to meet the short-term summer peak demands, and artificial recharge can be used to alleviate this constraint. In addition to meeting peak demands, artificial recharge can be used to bank the remaining portion of Nevada's unused allocation from the Colorado River for future use.At the present time (1988) the water supply for Las Vegas Valley is made up of ≈ 75% Colorado River water (about one-third of Nevada's 300 000 acre-feet consumptive use Colorado River allocation) and ≈ 25% groundwater, which is used primarily in the summer to meet peak demands. The District is investigating the feasibility of increasing the importation of treated Colorado River water into the valley during winter months, banking the water by artificially recharging the groundwater system, and subsequently withdrawing this water to meet summer peak demands and future needs.There were two major concerns regarding the feasibility of artificially recharging treated Colorado River water by deep aquifer injection. The first was the potential for calcite precipitation resulting from native groundwater and aquifer sediments mixing with treated Colorado River water which could reduce the aquifer permeability. The second was the long-term effects on well performance and production longevity by injecting through production wells.Although previous laboratory studies predicted that calcite precipitation would occur, a small-scale artificial recharge pilot study, conducted by the District in 1987, showed insignificant calcite precipitation. A larger scale demonstration project, initiated in February 1988, injected a total of 1153 acre-feet of treated Colorado River water into the principal groundwater system through two existing production wells. Injection was completed in late April and recovery of the native groundwater and Colorado River water mixture continued throughout the summer and fall. Recharge was accomplished by injection through the existing pump columns with minimal retrofitting of the existing wells and no detrimental effects to the pumps or well production rates have been determined. Water quality analyses and geochemical modeling indicate very little, if any, calcite precipitated during recharge and recovery.