ABSTRACTArtificially recharging the ground‐water system is one water resource option available to the Las Vegas Valley Water District in response to increasing water demand during summer peak periods. The existing water‐supply system for Las Vegas Valley is limited since peak water‐use demand periods in 10 to 20 years or less will require the construction of additional facilities. To prepare for these short‐term (and longer) demands, the Las Vegas Valley Water District, in cooperation with the U.S. Bureau of Reclamation, conducted a limited ground‐water recharge demonstration project using treated Colorado River water.A major concern of water managers regarding artificial recharge is the resulting water chemistry when treated (potable) Colorado River water is injected into the ground‐ water system. Both waters are high in calcium creating a potential for calcite precipitation which, in addition to clogging the perforations in the water well casing, could potentially reduce aquifer permeabilities by clogging the pore space of the flow media.Approximately 525,000 gallons of potable water were injected into a semiconfined ground‐water aquifer over a three‐day period interspersed with two pumping periods. Water chemistry samples taken throughout the injection project showed no imbalance with regard to calcium or any other chemical constituent. Therefore, artificial recharge is feasible and is one water resource technique available to meet an increasing water demand based on the existing water quality of the Colorado River and the quality of the ground water in the ar