by Charlene Burgi
It’s the top of the 9th and the Cardinals are up. The score is 9-0 with the Giants leading. There are two outs. The problem? What started as a gentle mist at the beginning of the inning has turned into a torrential downpour. One of the commentators exclaims that a person could hydroplane on the amount of water standing on the infield. I watch transfixed to see if the game will go on.
That final game of the National League Championship was a reminder that water applied too fast can cause puddling or flooding. Precipitation can be a problem on many levels, whether it is rain or irrigation. Despite the excellent drainage and soil preparation at AT&T Park, the precipitation rate was too great and those of us watching saw the flooded infield.
Whether rain or irrigation, precipitation rates are measured in inches. Weather reports give us the number of inches of rain that falls in a given time. And, likewise, irrigation manufacturers give us the inches that fall from our sprinklers in a given time. The difference is that we must live with whatever falls from the sky, but we can control the amount of water that falls from our sprinklers by the type of nozzles that we install.
For example, most pop-up spray nozzles will emit anywhere from 1.5 inches per hour to a whopping 6 inches per hour. Gear-driven rotors commonly found in large lawn areas will emit 0.2 to 0.8 inches per hour, but they are rare in residential landscapes. However, matched precipitation rotators emit 0.3 to 0.45 inches per hour. As you can see, the spray heads (nozzles) are putting down a greater number of inches than a rotator. The pop-up sprays work if you are applying that water on a level area for short periods of time and the soil is well prepared to receive that quantity of water. However, if your landscaped area is on a slope, or if you are irrigating an area that has heavy clay soil, your irrigation system could create run off and not penetrate into the root system.
By now, you are probably scratching your heads asking why I am addressing this issue when you know the irrigation system should be off due to recent storms. However, it is never too late to switch out the nozzles on your irrigation system. This is as simple as unscrewing the nozzles on your existing system and replacing them with nozzles that have a lower precipitation rate. Make certain that you change out all the nozzles on a station with the same manufacturer’s make and model, and install the nozzles that will provide the best coverage for the area. Just make sure you are getting head-to-head coverage so the throw of water from one nozzle will reach adjacent nozzles. Choose patterns that match the contours of the area being watered—that is, quarter, half or full heads. It is that simple.
The Giants won the National League Championship and made it to the World Series. Be one step ahead this spring by lowering the precipitation rates on your irrigation system if you haven’t already done so. The soil will absorb water at a deeper level. The roots of your plants will be thrilled and you, too, will score by not creating runoff and water waste!