Whiskey is for drinking - water is for fighting over: population growth, infrastructure change, and conservation policy as drivers of residential water demand

As urban populations grow, water managers are becoming increasingly concerned about water scarcity. Water managers once relied on developing new sources of water supply to manage scarcity but economically feasible sources of unclaimed water are now rare, leading to an increased interest in demand side management. Water managers in Las Vegas, Nevada have developed innovative demand side management strategies due to the cities rapid urbanization and limited water supply. Three questions are addressed. First, in the developed areas of the Las Vegas Valley Water District service areas, how did vegetation area change? To quantify changes in vegetation area, the Matched Filter Vegetation Index (MFVI) is developed from Mixture Tuned Match Filtering estimates of vegetation area calibrated against vegetation area estimates from high-resolution aerial photography. In the established city core, there was a small but significant decline in vegetation area. Second, how much of the observed decline in per capita consumption can be explained by Las Vegas land cover and physical infrastructure change that resulted from extensive new construction and new use of water conserving technology, and how much can be attributed to water conservation policy choices? A regression analysis is performed, followed by an analysis of three counter-factual scenarios to decompose reductions in household water into its constituent parts. The largest citywide drivers of change in water consumption were increased water efficiency associated with new construction and rapid population growth. In the established urban core, the most significant driver was declining vegetation area. Third, water savings generated by a conservation program that provides incentives for homeowners to convert grass into desert landscaping are estimated. In the city core, 82 gallons of water are saved in June for each square meter of landscape converted in the first year after conversion, but the savings attenuate to 33 gallons per meter converted as the landscape ages. Voluntary landscape conversion programs can generate substantial water savings. The most significant result is that the most effective way to ensure long term, sustainable reductions in water consumption in a growing city without changing water prices is to support the construction of water efficient infrastructure.