Keeping options open

Your region’s ample freshwater supply has historically simplified irrigation for commercial and residential properties. As an irrigation professional, you’ve likely taken for granted the ease of managing irrigation systems with a simple connection to the local water source.

Yet, during recent drought conditions, state and local government water agencies quickly enacted water shortage contingency plans and implemented restrictions on potable water use. California, for example, has a history of implementing strict water-use policies during drought periods. In recent years, tight restrictions on outdoor water use have been seen. Golden State cities like Los Angeles, San Diego and Sacramento have imposed limitations on outdoor water use, including landscape irrigation.

Throughout the American Southwest to counter water shortages, states and municipalities like Phoenix, Tucson and Las Vegas have imposed significant water-use restrictions during extended drought conditions.

Water restrictions aren’t limited to the Southwest. Recently parched regions along the East Coast like Georgia, Florida and South Carolina have countered drought with irrigation restrictions.

Water restrictions can vary significantly from state to state, within an individual state, or even within a single municipality. They often depend on factors like local water supply, population density and how those areas define drought conditions.

Sometimes, even when the threat of drought has passed, legislators are slow to reverse those restrictions. Almost overnight, irrigation pros find themselves seeking temporary or even permanent alternatives to potable water.

“Yes, there’s more pressure today to conserve potable water for human consumption, and the trend is definitely toward using nonpotable water for [landscape] irrigation.”
– Chuanxue Hong, Virginia Tech

“Yes, there’s more pressure today to conserve potable water for human consumption, and the trend is definitely toward using nonpotable water for [landscape] irrigation,” says Chuanxue Hong, a professor of plant pathology at Virginia Tech who has extensively studied water quality dynamics in irrigation sources and agricultural water health. “It started 25 years ago with farmers using runoff water to irrigate their crops.”

Water availability and the quality of water sources are becoming more challenging for landscape professionals, especially as water availability and allocations fluctuate or are outright restricted depending on drought conditions, says Donald Rainey, an extension regional specialized agent responsible for the Southwest Extension District water resource program at the University of Florida’s Institute of Food and Agricultural Sciences.

In Florida, where Rainey is based, this issue is impacting the development of new housing. “We’ve had [residential] communities stop building until other means of water supplies come in, and even the potable water for residents is sometimes in question,” he says.

Regardless of where you do business, a single extended drought can cut the flow of potable water and force landscape pros to find new sources of water. Here are some key areas to consider if you plan to tap into nonpotable sources to supply water for your commercial and residential irrigation clients.

What’s in the water

The suitability of nonpotable water for irrigation depends on its overall quality. Contractors must test and examine closely the chemical, biological and even physical properties of the water they are drawing from a nearby water source and the feasibility of treating it for irrigation purposes.

Nutrient levels — primarily concentrated nitrogen and phosphorus — should be the central area of concern for landscape contractors when assessing nonpotable water quality, says Hong. Both elements, critical components in fertilizer, enter water systems as runoff from surrounding agriculture or urban landscapes, but they can also be sourced from untreated or partially treated sewage overflows and even industrial wastewater. The concentration levels can vary greatly depending on where they’re sourced.

Excess levels of these nutrients in a water supply often encourage rapid algae growth. When algae die, they decompose, dramatically affecting water quality. This process consumes oxygen and releases carbon dioxide, causing the pH level to skyrocket to dangerously high levels, sometimes reaching pH levels of 10 or higher. At those levels, the water becomes toxic and aligns with some strong cleaning products, bleach and even ammonia.

“That’s very alkaline,” Hong says. “If a contractor puts that water back into the soil, it could change the nutrient availability [to the turf], or it could affect the performance levels of the pesticides being used, as well.”

If left untreated, highly alkaline water can cause scale buildup in irrigation pipes, reducing water flow and resulting in costly damage throughout the system, he says.

Elevated nutrient levels are detrimental to nonpotable water chemistry, says Isaya Kisekka, PhD, professor of hydrology and agricultural water management at the University of California-Davis and the director of the university’s Agricultural Water Center.

“When it comes to recycled water, there are things you need to pay more attention to in your irrigation water quality analysis, and the first one is the chemical composition of the water,” he says. “Recycled water is different from freshwater supplies in terms of its chemical composition. It may have heavy metals like lead and cadmium. You want to make sure that the composition of these chemicals is low and that they will not damage your [landscape].”

Even well water may contain elevated levels of calcium and magnesium, which can collect throughout an irrigation system and cause costly maintenance issues.

In addition to chemistry, untreated nonpotable water can be infested with pathogens harmful to turfgrass and even the people working with it. These pathogens could include turf disease issues like pythium and rhizoctonia, as well as dollar spot and brown patch, to name a few.

Salinity is another issue common with nonpotable water sources, and it’s not exclusive to coastal areas.

“This is especially problematic in regions where people have hard water and use softeners,” Kisekka says, referring to the process of replacing hard water minerals like calcium and magnesium with sodium ions. “Sodium is particularly dangerous to the soil structure and breaks down the aggregates, which then leads to sodicity problems.”

Kisekka explains that, in high enough concentrations, sodium ions disrupt the structure of soil aggregates, which decreases soil porosity, resulting in poor infiltration and drainage. This results in poor soil health and problems for the grass or other plant matter.

The researchers note that nonpotable water sourced directly from municipal water districts, while not cleared for consumption, is processed and decontaminated to a level that eliminates most pathogenic threats to humans and the landscape.

When irrigating with nonpotable water, you need more intentional, intensive monitoring and management than conventional potable water sources.

Soil health

When irrigating with nonpotable water, you need more intentional, intensive monitoring and management than conventional potable water sources. Monitoring plant and soil health is critical.

While visual observations of plant health provide a first alert on soil vitality, understanding nonpotable water’s impact on the soil is essential in mitigating larger-scale issues. For example, contractors must consider the leaching fraction to manage salts and other contaminants.

Kisekka explains that this is the water volume ratio that drains from the root zone to the total amount of water applied through irrigating with a nonpotable source. The rule of thumb is a leaching fraction of around 10% to 20%. However, an elevated figure increases water consumption for plant uptake, soil nutrient loss, soil erosion, and damage and strain to irrigation systems.

“This is how you manage contaminants in the soil profile,” he says. “Whenever you irrigate, you add more of those contaminants — salts and minerals — to your soil. Keeping those levels low will protect your soil and your [landscape] and your irrigation system.”

Lastly, Rainey says a region’s drought and flood cycles will have repercussions on not only the quality of what’s being pumped out of nonpotable sources but also the impact runoff may have on the surrounding watershed.

“In Florida, we could experience a storm surge that will directly affect water quality,” he says. “That then leads back to groundwater infiltration of saltwater and salinity levels. So, you need to understand that because it’ll impact how you apply that water [from an irrigation system].”

Contingency planning

Contractors must be in tune with the permitting requirements for tapping into nonpotable water sources for irrigation in their markets. To complicate matters, there is no one-size-fits-all solution. The proper permits to use nonpotable water to irrigate commercial and residential properties vary significantly based on where the contractor is doing business. In addition, factors such as local water regulations, the involvement of various governmental departments, property type and zoning, and the source of the nonpotable water (treated wastewater versus groundwater) may influence the permit process.

“Part of the permitting process involves engineering and understanding how much [water] you can pull out without affecting the surrounding [environmental] systems,” Rainey says. “In Florida, which I can speak directly about, the water management districts are highly regulated, and it’s meant to protect the watersheds. So, it becomes a much more holistic approach than just drawing water into an irrigation system.”

Rainey encourages contractors to consult with local water management professionals to better understand the complexities of water regulations and permits in a particular area. In addition, the process may involve developing a water management plan that outlines the property’s water source, treatment and irrigation practices.

While water restrictions haven’t been a major issue for many states east of the Mississippi River, Kisekka says on the West Coast and in the Southwest, people are coming to terms with the fact that they must do a better job managing their potable and nonpotable water supplies. There are valuable lessons here that everyone can learn from.

“Things like multiyear droughts are becoming a way of life and we must prepare for that and how we’re going to manage these water resources,” he says. “Even if you’re a landscape contractor in New Jersey, drought will find you in New Jersey.”

The unknown, especially regarding ever-changing drought patterns, forces irrigation professionals to devise a contingency plan to use the water they can access in the most efficient and effective fashion possible.

“Freshwater is not an endless resource,” Rainey says. “Here in Florida, we’re getting more incidents of isolated droughts, and they’re getting harder to predict. So, it’s best to have a plan on how best to use and protect the [freshwater] we have access to.”

Mike Zawacki is a freelance writer with nearly two decades of experience covering various aspects of the green industry, including the irrigation and lighting industries.