Satellite-based study of water demand reductions from urban landscape modification in Salt Lake City, Utah

Western U.S. cities are faced with limited water resources and rapid urban population growth, which creates challenges for urban and regional water managers. New water development is an expensive solution to water shortage problems, whereas water conservation, reuse and improving urban water use efficiency have become more advantageous and cost effective for eminent water shortages. Another innovative alternative is landscape modification. Low-water use landscaping is designed to conserve outdoor water used for irrigating turf grass in the desert. Past landscape modification studies have shown the effectiveness of this viable option, but these studies relate to specific geographic sites with varying climate impacts. In order for water managers to estimate the benefits of landscape modification in a semiarid mountain west metropolitan area, further analysis is needed to establish a relationship between outdoor water use and low-water Use landscaping. This thesis addresses this concept, using the Salt Lake City metropolitan area as a case study. This is done by using IKONOS and LANDSAT satellite datasets to measure the abundance of green vegetation depicted by the Normalized Difference Vegetation Index (NDVI). Monthly water use records were examined to develop seasonal outdoor water use patterns relative to the NDVI-based fraction vegetation per household. Low-water use landscape households were compared to traditional turf landscapes to quantify outdoor water conservation. On average, residents saved between 15-40% of their annual outdoor water use if they used low-water use landscaping. Higher annual outdoor water use savings near 65% were observed by residents who used low-water use groundcovers, mulch, and other desert plants throughout their yards. New city ordinances and rebate incentives will entice residents to adopt landscape modification and coordinately save water across the valley. Metropolitan scale applications indicate that approximately 7.1 billion gallons of water could be saved per year by converting turf grass to water efficient landscaping. Certainly, this is a viable solution to be considered by water managers in the western United States for immediate and long-term water shortage challenges.