Turfgrass and Drinking Water Waste in the United States / EPA Research Report on Turfgrass Allowance
On average, single-family homes in this country use 30 percent of their household water outdoors; however, in many areas of the country, outdoor water use ranges from 50 to 70 percent. For example, 60 percent of residential water is used outdoors in Phoenix, Arizona,4 and 70 percent of residential water is used outdoors in Las Vegas, Nevada.
Examining outdoor water use and finding ways to be more efficient is important because our demand as a nation is growing faster than our water resources can manage. Between 1950 and 2000, the U.S. population increased nearly 90 percent, while the amount of water used from the public supply increased by 208 percent. For example, in 1965, average daily water use in Georgia was 50 gallons per person. In 2000, the per capita use had risen to approximately 200 gallons per day, a large portion of which was used outdoors. Once considered a problem only in desert regions, water supply issues have become more common nationwide in less drought-prone regions such as Georgia and the Northeast. Even under non-drought conditions, at least 36 states have predicted water shortages by 2013. Not only does outdoor water use comprise a significant portion of residential use, it stresses existing water supplies by contributing to peak demand during summer months. During these hot, dry times, utilities must increase capacity to meet residential landscape irrigation requirements, sometimes as much as three to four times the amount used during winter months. For example, rain rarely falls in Austin, Texas, during July and August; as a result, the city’s overall water use increases by nearly 100 percent compared to winter use. Even in temperate regions of the country, peak demand occurs during spring and summer months. A study in a region east of the Mississippi River demonstrated that water use increased by one third during the spring to fall growing season.
Research suggests that turfgrass receives the highest percentage of the residential irrigation water in traditional landscaping. Several studies indicate that commonly used varieties of turfgrass require more water than many commonly used landscape plants. In addition, homeowners tend to overwater turfgrass. As a result, landscapes with large expanses of turfgrass generally use more water than those planted with a mixture of other plants such as groundcover, shrubs, and trees.
Many research studies show that turfgrass-dominated landscapes, typical of residential yards in the United States, use more water than those with a mix of regionally appropriate plants such as groundcover, shrubs, and trees. While many of these studies were conducted in the western United States due to the serious water supply issues facing those regions, water savings from switching to regionally appropriate landscapes are still expected elsewhere in the country. In Marin, California, a study of 548 dwelling units found a strong correlation between the perimeter of turf and water use. Researchers developed a multiple regression model of water applied to the landscape compared to the turf perimeter, turf area, and total landscape area. Results showed a very strong correlation (R2 = 0.91), with turf perimeter identified as the dominant independent variable. When comparing turf-dominated landscapes to those dominated by the water-conserving tree, plant, and shrub varieties, the researchers found that the turf-dominated landscapes used 54 percent more water than the mixed landscapes.