Irrigation Design Class 101

Here in the Midwest, irrigation is designed to supplement natural rainfall. It is not meant to supply all of the water that the golf course needs for a prolonged period. Unfortunately, we are in a prolonged period without a lot of natural rainfall. We are currently about three and a half inches behind the amount of rain we should have to this point of the year. Because of this, some of the deficiencies of our irrigation systems start to show.

At Huron Hills, the irrigation runs down the middle of the fairways. This is called "single-row" spacing.  We have two choices with this type of system, we can over water the middle in order to get the edges of the fairway adequate moisture. The other option is to water the center to the optimum moisture level. This leaves scallops of grass that receive much less water. As long as we still get occasional rainfall, these areas will turn brown, but they should not die.

A single row system is pictured below.

Each circle would have an irrigation head in the center. These heads are designed to throw water to the next head in the row, thus giving a more uniform spread of irrigation. The lighter green areas only get water from one head, and thus get only half the water they should get.

Most of the greens at Huron Hills have a "triangle spacing." This means that three heads cover the green. The benefit of this is redundancy, if one head is not working properly, the other two will still cover most of the green. It also evens out the edges separating the irrigated areas from the non-irrigated areas.

This is an example of triangle spacing. (Ed: I noticed that my picture has a small error. The labels on this should be: No Water, 33% Water, 67% Water and 100% Water.)

With this type of system, you need more irrigation heads as well as twice as much underground piping, but the distribution is much more even. Keep in mind that the irrigation heads we use on the golf courses throw about 70 feet, so you can have the heads on each side of the fairway and keep most of the shorter grass under the dark green area in the picture above.

Most of what we have at Leslie Park Golf Course is "square spacing." In this system, the heads are set out in a square. This gives the most even distribution in between the heads, as you can see in the illustration below.

In order to make the picture more understandable, I exaggerated the space that gets 75% water in the middle of the fairway, in general, this will give a even distribution of water between the irrigation heads. Also, this is under perfect conditions with brand new equipment. The irrigation at Leslie was put in during the 90's. In all honesty, I do not know when the irrigation at Huron Hills was put in, but it is considerably older than that. As such, we have to keep track of any problems we find and fix them as soon as they crop up. That means keeping an eye on about 600 irrigation heads at Leslie and 200 at Huron.

In this photo, taken in 2012 of #4 fairway at Leslie, you can see a spot in the middle of the fairway where a single head was not operating properly. The other three head covered that spot to around 75% of what the grass needed. You can also see how the rough, which is outside of the square spacing of our irrigation, has turned brown and dormant.