LOCATING TURF AND WATER FEATURES IN THE LAS VEGAS VALLEY, NEVADA, USING REMOTE SENSING TECHNIQUES AND GIS

The Southern Nevada Water Authority (SNWA) was established in 1991 by the State of Nevada to secure future water resources of Southern Nevada communities, including the fast-growing city of Las Vegas. Part of this effort involves conservation of water in this dry desert community. Nearly 70% of water consumed is due to outdoor use—primarily irrigation of turf (grass). Additionally, some water is lost to evaporation from surface sources, including man-made water features such as swimming pools. SNWA has established programs which offer incentives to water consumers to reduce turf area in landscaping and to use swimming pool covers. In order to market conservation programs to the appropriate consumers, object- based and pixel-based image classification techniques were used to identify turf and swimming pools in the Las Vegas Valley. High resolution (6 inch), 3-band color infrared digital aerial imagery was collected in June of 2006 over the Las Vegas metropolitan area and surrounding communities. Using ERDAS Imagine™, a single band "diversity layer" was produced from each images' DN values and this layer was stacked into the three band CIR image. Visual Learning Systems' Feature Analyst™ extension for ESRI ArcGIS™ (9.1) was used to classify vegetation into trees, turf and shadows. An overall accuracy of 92% confirmed that SNWA could have confidence in the final dataset. A normalized band difference was used to determine the location and area of swimming pools and man-made ponds and lakes in the Las Vegas Valley. A GIS and "decision-based" geo-processing produced a "clean", final swimming pool dataset. GIS and common geo-processing tools were used to examine the relationships between vegetation layers, swimming pool data and existing municipal data. This allowed for identification of high-density turf neighborhoods and properties with swimming pools, and enhanced target-marketing for SNWA's turf-reduction and pool cover programs.