Urban water use is an increasingly significant portion of total water use, particularly in the arid West and rapidly increasing in the South and Mid-Atlantic regions of the U.S.  The major component of urban water use is for the irrigation of the urban landscape. Across the North America, 60% of residential water use is for outdoor use, primarily for landscape irrigation. Virginia’s Department of Natural Resources has noted “The greatest potential reduction in water use would come from reducing outdoor water use for landscaping.” Improvements in the efficiency of landscape irrigation could offer considerable potential for water conservation in the urban sector.

     A new type of lawn and landscape irrigation sprinkler, a multi-stream, multi-trajectory rotating(MSMTR) sprinkler, appears to offer improved distribution uniformity compared to fixed spray heads and rotors in sprinkler systems for lawn and landscape irrigation. Improved uniformity could mean higher irrigation efficiency, and potential water conservation.

     Kissinger and Solomon(2008) supported that anecdotal evidence with an analysis of 13 zones on a standard lawn and landscape irrigation system. They found that replacing fixed spray heads and rotors with MSMTR sprinklers(making no other changes) improved distribution uniformity(DU) by an average of 27 points, resulting in water savings of from 22% to 41% depending on pre-conversion irrigation management practice.

     Fixed spray heads and rotors, frequently used in lawn and landscape sprinkler systems, produce a static or rotating spray, distributing water over their entire arc of coverage. These may be installed on risers or in “pop-up” heads, which rise when the water turns on.

     Multi-stream, multi-trajectory rotating(MSMTR) sprinklers distribute water in a number of individual streams, of varying trajectories, which turn slowly. These sprinklers are the size of spray nozzles and thread onto pop-up heads just as spray nozzles do. They can also be threaded onto shrub adapters for installation onto risers.

     To investigate the water conservation potential of MSMTR sprinklers due to improved uniformity, audits were conducted on a variety of existing lawn and landscape irrigation systems employing fixed spray heads and rotors. The audits were conducted according to the protocol recommended by the Irrigation Association. The lawn and landscape sprinkler systems were first inspected and any obvious deficiencies(such as missing nozzles, broken pipes, leaking fittings) were corrected. A catch-can test was performed to determine the uniformity achieved by the fixed spray heads and rotors. Then the irrigaton systems were converted to the MSMTR sprinklers and a second catch-can test was conducted. A total of 51 audits were conducted.

     For 37 of the zones audited, the head location, spacing and other operating conditions were the same during each pair of catch can tests, except for the sprinklers used. In 14 zones, based on the improved coverage of the MSMTR sprinklers, some of the pre-existing spray head locations were eliminated; fewer MSMTR were used to cover the same area previously irrigated by a greater number of spray heads. In 7 of the 14 zones, the reduced number of head positions required some adjustment in the location of the remaining positions. In no case was the spatial density of head locations increased for MSMTR sprinklers.

     Results for the 51 zones audited were collected and analyized. In general, the uniformity of the existing lawn sprinkler systems using traditional fixed spray heads and rotors was not good. Overall, the MSMTR sprinklers achieved higher uniformity than the fixed spray heads and rotors. An irrigation manager’s response to dry spots and turf areas of poor visual quality should be to make changes that result in higher uniformity, rather than to increase lawn and landscape sprinkler system run times. Higher uniformity will enhance water conservation and reduce deficits as well. An irrigation manager may respond to dry spots and turf areas of poor visual quality by increasing lawn and landscape sprinkler system run times. However, setting run times at a higher rate on lawn and landscape sprinkler systems requires that considerably more water be applied, thus water conservation decreases.

     The recommended approach when encountering poor uniformity is to make the changes necessary to eliminate the uniformity problems, not to increase run times of the sprinkler system in an attempt to reduce or eliminate dry spots. Reducing deficits by increasing run times requires considerable extra water, but reducing deficits by improving uniformity actually achieves significant water conservation. If you have a uniformity problem, fix it-don’t drown it. EcoLawn Sprinkler System has installed many of the new MSMTR irrigation systems. Please call EcoLawn Sprinkler System today so that you may understand the water savings these new lawn sprinkler systems achieve.