 John Ossa |
Sprinkler and rotor manufacturers are focusing on three things: efficiency, features that create the potential for conservation and contractor education. Efficiency comes from nozzle design and pressure control that optimizes the dispersing of small, medium and large droplets over near, middle and far distances. In rotors, nozzle design typically works as follows: the objective is to send the most water as far away from the sprinkler as possible. As the distance from the sprinkler increases, the amount of area covered increases greatly. To “shoot” water to the end of the radius takes a high velocity and a trajectory somewhere between 20 to 35 degrees from horizontal. As the water passes the peak of the trajectory and begins falling, the large drops begin to break up into smaller drops. Simple physics determines that larger drops maintain a higher velocity and are least likely to be deflected by wind. The mid-range distance from the nozzle gets some water that’s “peeled” from the primary stream by mechanical means such as a dispersal screw, and, to a lesser extent, the outer layer of the stream – through friction with air – becomes unstable and breaks away. With larger rotors, the near distance usually is addressed by a separate nozzle designed to disperse smaller drops at less velocity that quickly fall to the ground. Most nozzles do a better job of sending water to the end of the arc, which highlights why head spacing with overlapping coverage is absolutely critical to the uniform application of water. Head spacing should never be stretched beyond the recommended nozzle radius. All of the principles described for the rotors apply to sprayhead nozzles as well. Part of the Answer There are new sprayhead nozzles on the market that achieve higher levels of efficiency than was previously possible. Toro won the Irrigation Association’s New Product of the Year (2008) with the introduction of its Precision Series Spray Nozzles. A fundamentally different approach to water dispersal achieves a 30 percent reduction in precipitation rate, matched precipitation and better definition to the edges of the spray patterns. The reduction in precipitation rate is significant because it provides more opportunity for water to infiltrate without run-off. Another approach to higher application efficiency is Hunter’s MP Rotator. These multistream nozzles have a low precipitation rate and are relatively wind resistant. They offer an excellent and much needed option in 14- to 30-foot radii. Nozzle families that have matched precipitation rates are vital to efficient irrigation. That inherent potential will be fully realized when the scheduling of the run times matches plant water need, which changes throughout the year to coincide with the length of days and average temperatures. Manufacturers are resegmenting their product lines for an evolving market created by municipal efficiency mandates and conservation requirements. They are refining key features that aid conservation. These features include in-head check valves, in-stem pressure regulation and specialty features like Toro’s X-flow device, which will sense if a nozzle is removed and shutdown water flow. Conservation is achieved by how the hardware is utilized. To capture all the potential for conservation requires an understanding of the basics. Manufacturers are increasing their commitment to contractor education to enhance the opportunity for their hardware to be put to its best use. For example, Rain Bird’s Web site offers a range of free how-to pieces, as well as tools that help forecast and quantify water savings. These and other manufacturers’ similar offerings educate and help the contractor sell efficiency to the end user. As an industry, what we need to sell is water management efficiency, not just pipes and hardware. |
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