UNDERSTANDING SPRINKLER COVERAGE

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1 HYDROBULL No 1 A TECHNICAL BULLETIN from HYDROGOLD INT'L WATER MANAGEMENT CONSULTANTS Copyright: Provided Hydrobull is distributed intact, it may be freely distributed. Hydrogold Pty Ltd retains copyright. Full terms are at: Back issues are available on our web site Hydrogold Pty Ltd - HYDROBULL is a technical bulletin covering issues related to water. Feedback is welcome: server@hydrogold.com Subscribe or unsubscribe at: UNDERSTANDING SPRINKLER COVERAGE There are 3 basic irrigation parameters: F Area of Coverage - The area watered by (in this case) sprinklers F Peak Application - The maximum application (precipitation) for the hottest period F Watering Window - The time period during which the irrigation occurs Sprinkler coverage has the single-largest impact on both the look of the golf course and the budget. 1 HEAD TO HEAD COVERAGE, PERCENTAGE SPACING & UNIFORMITY The throw of the sprinklers is the effective distance to which water is thrown from the sprinkler. Typically, the spacing between the sprinklers is equal to the throw. This is referred to as "Head to Head"; where one sprinkler (Head) throws to the adjacent sprinkler (Head). For a variety of reasons, this Head to Head spacing may be stretched (typically to reduce the number of sprinklers and therefore the budget) or shortened (typically for wind). To allow comparison, the irrigation industry talks of "Percentage Spacing". Percentage Spacing is the ratio of the sprinkler spacing TO the diameter of sprinkler throw expressed as a percentage. That is: Sprinkler Spacing Percentage Spacing = 2 x Radius of Throw *100% Head to Head spacing (Sprinkler Spacing = Radius of Throw) is therefore 50% Spacing. What happens when we stretch to a 55% sprinkler spacing? Eg. A 20 m (66 ft) throw sprinkler and spaced at 22 m (72 ft). In a triangular grid it would most likely be OK provided you had next to no wind (less to 5 km/h or 3 miles/hour) and a good sprinkler. What happens when we stretch to a 70% sprinkler spacing? Eg. A 20 m (66 ft) throw sprinkler and spaced at 28 m (92 ft). The result is highly non-uniform irrigation (wet and dry spots); the legendary (greener) donut with a yellow (dry) area around the sprinkler. Refer to the right hand sprinkler plot over page. In summary: The Percentage Spacing is critical to the efficiency of sprinkler irrigation systems and the budgets. It needs to take account of the wind and the actual sprinkler nozzle performance. Utilise Hydrogold's experience to make the right decision. Hydrobull No 1- Understanding Sprinkler Coverage Page 1

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3 2008 Hydrogold Pty Ltd HOW MUCH COVERAGE? Having decided on our sprinkler spacing, we need to consider the area of coverage. The irrigation system has the single-largest impact on the look of the golf course so the involvement of the Golf Course Architect and the Owner is critical. There is also the consideration of budgets and water requirements that Hydrogold provides critical advice on. It is almost universal nowadays to consider the irrigation of Greens, Tees and Fairways (the "in-play" areas) as a minimum. The thought of not watering fairways has never been seriously considered on any of the golf courses that we have been involved with. The main consideration is how wide the irrigation is. That is, how far does it extend into the rough. For the purposes of general discussion, we will consider the following: 2.1 Single-Row Sprinkler Coverage (refer to sketch No 407-A4 following) This type of system is only included for completeness. The single-row sprinkler coverage would only be considered under extreme budget pressure. It has poor uniformity so cannot be used on the grounds of conserving water. In Hydrogold's experience, this would be used on less than 1% of golf courses. 2.2 Two-Row Sprinkler Coverage (refer to sketch No 409-A4 following) For modern golf courses, a two-row system would be considered a minimum. It provides adequate coverage for in-play areas unless there is wind. It is not suitable for wider fairways. 2.3 Three-Row Sprinkler Coverage (refer to sketch No 411-A4 following) Nowadays, this is considered fairly typical of the needs of an average golf course. The in-play areas receive a good uniform coverage which provides an efficient irrigation system. 2.4 Wall to Wall Sprinkler Coverage (refer to sketch No 413-A4 following) This type of coverage is reserved for up-market (say top 15% of) golf courses providing a vista of green wherever you look. This type of system is also able to implement water-conserving strategies effectively during periods when the water is scarce. Eg. The "Wall to Wall" irrigation system designed by Hydrogold in Singapore for Tanah Merah Country Club's Garden Course in Singapore - Golf Course Architect - Phil Jacobs Hydrobull No 1- Understanding Sprinkler Coverage Page 3

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8 2008 Hydrogold Pty Ltd OTHER AREAS TO CONSIDER FOR SPRINKLER COVERAGE The sprinkler coverage is THE major consideration on a golf course (see section 2). Aside from the discussion of the in-play areas, there are other significant considerations: 3.1 Driving Range Nowadays most driving ranges are irrigated to attract Golfers to the facility, a significant revenue stream. 3.2 Area Between the Fairway and Buggy Path This is normally a high traffic area with buggies being driven from the path onto the fairways. It is essential this area is irrigated so that the turf can regenerate from the wear of the buggies. 3.3 Club House Surrounds Particular attention should be paid to vistas from the Clubhouse. This is the place where Golfers and cameras take time to look at the golf course. Typically areas visible from the Clubhouse should be considered for irrigation. 3.4 Irrigation of Mounds Mounds are often used at the back of bunkers or to separate fairways. Being high points, they are highly visible. Irrigating them, especially where they are prominent in views such as those from the Clubhouse, is desirable. 3.5 Transition Zone from the Green to the Next Tee After playing a nice wide, green hole, the Golfer is not likely to appreciate driving through a dry, barren area to the next tee. The drive from the Green to the Next Tee is an important area that contributes to the experience of the Golfer and should be considered for irrigation. 3.6 Entry Drive The drive into the golf course raises (or lowers) the expectation of Golfers arriving at the golf course. Entry Drives should be well irrigated to enhance the views for people arriving at the golf course. 3.7 Waste Bunkers Sometime (in areas such at the Middle East), there are large "Waste Bunkers". Depending on the situation with wind, the irrigation of these bunkers (or perhaps protection berms) may be needed to stabilise the sand. Waste Bunkers on Ernie Els' Victory Heights Golf Course in Dubai - Irrigation by Hydrogold Hydrobull No 1- Understanding Sprinkler Coverage Page 8

9 2008 Hydrogold Pty Ltd SPRINKLER COVERAGE AND WATER CONSERVATION Just because you have the sprinklers does not mean that you have to use them all the time. Eg. For a three-row system during a time of low water availability, the middle row could be operated and the outside rows could be switched off. Provided the control system is properly designed, this is as simple a choosing another irrigation program at the Computerised Central Controller. This is preferable to hand-watering (see later in this article). If designed correctly, irrigation systems with wide coverage offer flexible and effective management for water conservation. 5 SPRINKLER COVERAGE AND HAND-WATERING One of the thoughts put forward is to have a "skinny" irrigation system and to just hand-water areas such as the back of a bunker. Would an accountant ever suggest leaving out 2 sprinklers (saving say US$ 1,000) and doing occasional hand--watering? The area of 2 sprinklers will take at least 30 minutes of labour each time to water. Say we do that 50 times a year (once a week) for 20 years (typical life of a well-designed irrigation system). Say labour is cheap at U$ 10 an hour. So the cost of the occasional hand-watering is US$ 5,000 (=(30/60)*50*20*10). And on top of that hand-watering is: F A day-time nuisance to Golfers (the revenue stream of the golf course) F Another supervisory task for the Golf Course Superintendent F Inefficient irrigation (wasteful of water and electricity) 6 AND FINALLY - THE SPRINKLER COVERAGE PLOT At Hydrogold, we believe the sprinkler plot is the single-most important part of the irrigation design process. The sprinkler plot shows: F The outline of throw of each sprinkler in a dashed circle or arc F Exactly what areas will be watered and what will not be F If sprinklers are overthrowing roads or buildings This is the information that the Golf Course Architects and Owners are most interested about the irrigation system. Involving them in the design process ensures that the design meets their needs. From this, preliminary budgets can be made to ensure no rude shocks to the Owner later in the design process. A sample sprinkler plot is provided over page. A full A0 Overall Layout (which shows the sprinkler coverage plot) is available on Hydrogold's web site ( under the on-line documentation. Hydrobull No 1- Understanding Sprinkler Coverage Page 9

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