Irrigating responsibly: Recycled water and turfgrass irrigation

As populations around the world rise, more people are moving to large metropolitan areas. Often called concrete jungles, these urban centers actually contain most of the world’s turfgrass. Despite the many positive effects of turfgrass in urban landscape, it competes with human consumption for access to clean irrigation water. The high demand and rising costs of clean water is putting pressure on urban areas to find another answer to their water woes.

“In Southern California, as in much of the southern and southwestern US, we’re dealing with serious water shortages,” says Dr. Ali Harivandi, an environmental horticulturist with the University of California cooperative extension. “And it’s not even about drought. There are just too many people and not enough clean water.”

A potential solution to this problem is the use of recycled water, water that has undergone a cycle of human use before being treated at a sewage treatment plant. There are different degrees of treatment (primary, secondary, or advanced) that result in recycled water suitable for different purposes, including turfgrass irrigation. Already, 15% of U.S. golf courses and nearly 35% of courses in southwestern states have turned to recycled water as their source of turfgrass irrigation.

Golf ball and tee

Currently, some small risks of direct human consumption of recycled water do exist. Pharmaceutically active compounds (PhACs), for example, often evade treatment methods and remain in recycled water at very low levels. These compounds come from drugs and personal care products that can enter our water supply after being flushed in the toilet or washed down the sink. “Those pharmaceutical compounds in water don’t really affect plant life, but we know that they can have effects on humans and animals,” says Harivandi.

Due of the health concerns associated with recycled water, most cities are required to inform the public if recycled water is being used in their community. Purple has become the official color of recycled water, with almost all recycled water irrigation equipment (pipes, sprinkler heads, valves, ect.) now available in the color. 

As treatment technologies have advanced and we have learned more about recycled water and its safety, turfgrass irrigation has emerged as an ideal application for water reuse. Turfgrasses can absorb large quantities of nutrients, a trait that pairs well with the high levels of nitrogen often found in recycled water. And because turfgrass isn’t consumed by humans, water reuse on turfgrass poses little risk of transferring harmful pathogens to humans through the food chain.

Still, the high levels of dissolved salts that most recycled water contains can pose problems for turfgrass health. High concentrations of salt accumulation in soil can lead to leaf burn and leaf death, and may prevent water absorption by plant roots. Some elements found in recycled water, including sodium, chloride, and boron, are toxic to turfgrass and other plants at certain levels of concentration. Turfgrass managers can do to some things mitigate these problems, like plant salt-tolerant turfgrass species, increase irrigation, and install proper drainage systems.

Harivandi says that the stigma attached to recycled water has always been a challenge for the industry, and will continue to be in the future. “In the northern part of the country, people really haven’t been using this water much,” he says. “The only thing they can think about is the water they flush down the toilet in the morning.”  

Once we get over that, recycled water may become a valuable alternative to limited and costly potable water, and as populations around the world continue to rise, turfgrass sites in urban areas will likely expand. The potential recycled water has to irrigate these sites suggests that it will play an important role in our future.