Water Use and Conservation in Urban Landscaping Activities: The Case for Graywater Utilization

Among the various uses of water in urban settings, landscape irrigation is a top contender, with reports indicating that over 50% of residential water use in the United States is devoted to irrigation of lawns and gardens. We have estimated that there are about 1.4 million acres of irrigated landscapes in Texas. Considering an average irrigation rate of 30 inches per year, this represents a total water use of about 3.5 million acre-feet per year, corresponding to about 20% of the total projected annual water demand by all activities in Texas in 2010. Due to current and future projected drought, challenging water competition and imminent restrictions on urban water use, there is a strong need for implementing water conserving practices and utilization of alternative water sources in landscaping activities. Graywater, defined as untreated water that comes from clothes washers, showers, bathtubs and sinks, constitutes 50-65% of the total wastewater generated by a household, and offers the potential for becoming a significant water source for landscape irrigation. The average volume of graywater generated at a typical household could potentially provide for 50% of the irrigation needs of an average-sized landscape utilizing xeric (low water use) plant materials. This premise is contingent upon the identification and use of suitable plants that can provide the aesthetic and functional value of urban landscapes with the utilization of these alternative irrigation sources, as well as the practical and cost-effective engineering considerations to make this viable for both new and existing housing. Our team has initiated research, demonstration and educational activities to provide answers and practical solutions to the implementation and adoption of these water-conserving practices.