Irrigation: cost or investment?

Previously we talked about some of the reasons commonly put forward for not watering bowling greens. I also shared with you, my amusement that so many clubs fail to mention irrigation or lack of it when looking for an explanation for the poor quality or condition of their greens; even though it’s very obvious. They will use just about every other aspect of bowling green maintenance as a reason for poor performance.

Now we come to the cost of irrigation; and I am not talking about the cost of installing a system, but merely the cost of the water being applied on any given night.

This is another big reason or excuse that I hear a lot about:

“we can’t water any more because it costs a fortune”

Now of course there will be variations (slight) around the country and also from system to system, but here is my 10 second rundown on the cost of water for irrigation:

- As we saw previously a typical system will put out 1mm of irrigation water for every 2 minutes of system run time.
- A typical system will also put out 150 litres per minute; so to calculate the cost per mm of irrigation we do this:
- 2 (minutes) X 150 (litres) X 4 (sprinkler heads) = 1200 litres/mm

That’s to achieve 1mm over the whole green.

As 1200 litres is 1.2 m^{3} you simply have to multiply the irrigation requirement in millimetres by your cost per m^{3} and then by 1.2

Example:

- Water balance sheet shows we need to replace 15mm of moisture loss.

- Multiply 15 (mm) X 1.2 (m
^{3}) X £/m^{3}

- 1.2 (m3) X £0.90 = £1.08/mm of irrigation over entire green.

I’ve used 90p as an average cost, but you can find your own local charge on your water bill or by phoning the water company.

The question is whether you see irrigation as a cost or an investment in the future of your green.

Hi John,

A question on irrigation of a bowls green. We have a 3 rink Bowls green that measures 20 mtrs by 40 mtrs. We water by using an

Orma Leader 20/40 reel irrigator. Our water is mains supplied and gives us 30 Ltrs per minute. The sprinkler system automatically travels up the green and we have set the travel time at 4hours. How do l calculate the water coverage.

Sid GUICHARD

Captain Whiteley Village Bowls Club.

Hi Sid

This can be calculated as follows:

First, let’s convert the time the sprinkler was running from hours to minutes, since the flow rate is given in litres per minute.

4 hours = 4 X 60 = 240 minutes

Now we can calculate the total volume of water output by the sprinkler:

Volume (in litres) = Flow rate (in litres/minute) x Duration (in minutes)

= 30 litres/minute x 240 minutes

= 7200 litres

Now, to convert this volume to a depth in millimetres over the given area, we use the formula:

Volume (in mm) = (Volume (in litres) / Area (in square meters)) x 1000

= (7200 litres / 800 square metres) x 1000

= 9 mm

So, the sprinkler applied a volume of water equivalent to a depth of 9 millimetres over the 800 square metre area. Approximately 3 days worth of Evapotranspiration, working on the premise of 25mm per week

Regards

John