Texas A&M AgriLife Research ornamental horticulturist Dr. Raul Cabrera is hoping to generate popular interest in using “graywater” to irrigate home landscapes. Graywater, Dr. Cabrera explains, is essentially “soapy” water left after tap water has been run through a washing machine or used in a bathtub, bathroom sink or shower and does not contain serious contaminants. He suggests that while it is of course difficult to precisely estimate Texas’ statewide potential for water conservation through use of graywater and application of the technology needed, he suggests that graywater conservation could reduce household landscape water use by 10 to 25 percent or more, subject to size, type of landscape plants used, and geographical location.
“The average household uses as much as 50-60 percent of its water consumption for the landscape — grass, ornamental plants, trees, etc.,” Dr. Cabrera comments in an article by Agrilife Today’s Paul Schattenberg. “Considering that the average family of four produces about 90 gallons of graywater per day, if this was used to irrigate a landscape, it could represent a significant water savings.”
Dr. Raul Cabrera joined the Horticultural Sciences Department in 1999, and has been a member of the graduate faculty at Texas A&M University since 2000. He was stationed at the Texas Agrilife Research and Extension Center in Dallas, and since 2012 he is stationed at the Texas A&M AgriLife Research and Extension Service Center in Uvalde.
Texas AgriLife Research is a partner in the newly established Water Conservation and Technology Center (WCTC) based in San Antonio. The WCTC’s objective is to accelerate development and adoption of new and innovative technologies to solve emerging water problems and meet future water supply needs. The center is establishing a team of scientists, engineers and water professionals dedicated to accelerating the development and adoption of technologies for water conservation needed to meet the water demands and economic growth of the future.
Texas AgriLife Research, Texas AgriLife Extension Service, Texas Engineering Experiment Station and Texas A&M University-San Antonio are working together to integrate strong public/private partnerships that will focus on applied research and development, testing and validation, technology transfer and training and extension education in water conservation, water re-use, groundwater desalination, energy development and water use.
The ornamental program at the Texas A&M AgriLife Research center, Uvalde, is helping green industries to improve water-use efficiency through emergent research on native and adapted plants using graywater and other alternative irrigation sources. Dr. Cabrera along with colleagues from the Uvalde center and the Texas Center for Applied Technology began research in late 2012 to confirm the potential use of gray water for home landscape irrigation. Texas AgriLife estimates that integrating deficit irrigation strategies (75% ETc) with specific crop coefficients and improved cultural strategies, can improve water use efficiency (up to 25%) in cool season leafy vegetables.
“We wanted to find out whether or not using graywater to irrigate home landscapes would be a practical thing to do based on its effects on various ornamental plants,” Dr Cabrera is cited explaining, “So we set up an experiment to irrigate various ornamental plants using different types of graywater…. You don’t usually see a washing machine in a greenhouse, but we had one installed so we could run loads with detergent alone, then loads with detergent and fabric softener, then a load with bleach. This way, we could produce and use different types of gray water and see how it might affect the growth and aesthetics of different ornamentals, particularly since there would be different chemicals in the water, depending on the detergents and cleaning agents used.”
Experimenting with what were deemed the most popular domestic brands of detergent, fabric softener and bleach,using each according to its manufacturer’s recommendations, Dr. Cabrera notes that after two and a half months of irrigating various ornamentals with different types of graywater, initial results based on visual inspection of the plants are mostly promising, with a few exceptions — such as a few of the plants irrigated with the gray water containing bleach in the recommended amounts for laundry showing signs of yellowing and reduced flowering.
The researchers are also evaluating concentrations of other chemical constituents in graywater that could be harmful for plant growth, like sodium and boron.” However, gray water containing bleach was found to have little effect on most of the ornamentals used in the experiment, particularly hardier plants like holly, yucca and agave, and there was also no significant negative impact noted on any of the ornamentals from the graywater with detergent or detergent and fabric softener combination.
Dr. Cabrera believes this research is particularly relevant for drought-prone Texas as it may reduce household landscape water use by as much as 10-25 percent or even more, and that implementing the use of graywater for landscape irrigation across the state could mean a tremendous water savings in terms of acre-feet of water, contributing to the statewide water use and conservation goals of the 2012 Water Plan. He notes that most information on graywater use for irrigation is anecdotal, with little actual scientific research on its effects on landscape plants having been done previously.
The first phase of greenhouse graywater irrigation trials will continue for another two months, after which a second phase involving establishment of an outdoor landscape at the center will commence with the planting of trees and shrubs along with flowering and bedding plants in order to examine medium- and long-term effects of gray water on them over a two-year period. Dr. Cabrera says the researchers are very interested in determining the effects of gray water use on physical, chemical and biological characteristics of the landscape soil, how well such a drip irrigation system performs, and what kind of maintenance it might require when running gray water through it, thereby providing the sort of information needed by city planners, water-system administrators, and municipal, county and state officials for the purpose of officially permitting and promoting use of graywater as a significant urban water conservation strategy.
He also hopes to inspire support by other agencies, groups and organizations, and an eventual statewide initiative to encourage use of graywater for home landscape irrigation.