Is it really all about sprinkler counts?

Brian Vinchesi

Lately we have been hearing about sprinkler counts on golf course irrigation systems and that if your course installs fewer sprinklers, it will use less water. Although intuitively it makes sense in applicability, it is far from the truth. Unfortunately, many environmentalists, politicians, regulators and the general public understand the simplicity of less sprinklers/less water and therefore promote the use of fewer sprinklers. Fewer sprinklers is now considered to be more green and more sustainable.

Please pardon a little math, but if an irrigation system has 500 sprinklers using 40 gallons per minute operating for 20 minutes each, that’s 400,000 gallons of water. If I only have 400 sprinklers, then it is 320,000 gallons. Makes sense on the surface, but let’s delve deeper. In golf irrigation design, using fewer sprinklers requires larger sprinklers to be used to have acceptable coverage. The larger they are, the more water they use, the more pressure they require, and the less efficiently they apply water. Using more sprinklers to provide the same or more coverage is accomplished with lower pressure, less gallons per minute, a shorter throw and higher water application efficiencies. Let’s say you want to apply 0.10 inches of water. If the large sprinklers (80 foot throw) use 37.2 gpm at 80 psi with 65 percent efficiency and the 500 sprinklers (65 feet) use 22.9 gpm at 65 psi and are 80 percent efficient, what do the water use numbers look like? The 400 sprinklers are using 245,275 gallons to apply the 0.10 inches of water while the 500 sprinklers are using only 165,144 gallons. The math shows more sprinklers are using 33 percent less water. This could be the difference between single-row and double-row fairway irrigation for example.

The larger sprinkler count also has several other advantages. As outlined above, the greater number of sprinklers at the closer spacing operates at less pressure. This requires less horsepower to move the water, resulting in less energy use and less wear and tear on the pump system and its components. Having more sprinklers also provides for more control. Because each sprinkler covers less area, then you have control over less turf with each sprinkler. More control provides for better turf conditions and even more water savings.

It is easy to understand that less irrigated acreage and drought tolerant varieties of turfgrass equal less water. Although not true, it is easy to comprehend fewer sprinklers use less water. However, lacking in any discussion of sprinkler counts is sprinkler efficiency, spacing and uniformity. In sustainable golf discussions there is too much focus on the number of sprinklers, which if you know what you are talking about means nothing, and not how the sprinklers apply water. Covering the same irrigated area with closer spacing and more sprinklers is a much more efficient use of water than just broadly broadcasting the water. The less-sprinklers philosophy is just less area covered to save water with fewer sprinklers and as a result irrigation systems that are very inefficient. We should be less concerned about quantity and more concerned with the level of control within the irrigation system.

Control is the key. The more control you have over the water, the less water you will use and the more targeted the irrigation application. The trend in golf irrigation design is to have more sprinklers and that trend will continue despite the Pinehurst example and the discussion it has initiated. More sprinklers allow different types of turf to be irrigated differently and so specific water requirements of the varied cultivars can be individually targeted and applied. The more we can pinpoint the water application and not widely broadcast the water, the lower the water use and better the playing conditions. Short term the costs are higher, but long term there are many benefits and decreased costs.

Brian Vinchesi, the 2009 EPA WaterSense Irrigation Partner of the Year, is president of Irrigation Consulting Inc., a golf course irrigation design and consulting firm headquartered in Pepperell, Mass., that designs irrigation systems throughout the world. He can be reached at bvinchesi@irrigationconsulting.com or 978/433-8972.