ET is the combination of evaporation from the soil surface and the transpiration from the turf plant. The ET is the amount of water used by the plant in a 24 hour period accounting for wind, humidity, temperature and solar radiation. Our goal is to replace the amount water used in a single day.
The height of cut also makes a difference in the rate at which water is used by the plant. The lower the cut the more evaporation loss from water applied. As the height of cut increases, the evaporation portion of the plant water use decreases. Transpiration from the plant increases as the plant gets bigger. The relationship between the two values is not equal. That is why the larger plants will use less water. We expect to see some savings with the new height of cut in the fairways.
The way many people apply water today is by using time intervals. Watering 5 to twenty minutes per station per night is common practice. Our computer uses ET so we can water to the second, replacing the water used that day. The computer’s database contains information about each head’s makeup. Gallons per minute, area covered, arc pattern in degrees and spacing with other heads to calculate a specific precipitation rate for that designated head. This information was what we were working on three years ago to make sure the computer could accurately make watering decisions using the ET. Each night the run time is changed to meet the plant’s water usage and throughout the year adds up to a sizeable amount of savings due to the accuracy of water application.
The central control system that we use is by far, one of the most important and most powerful tools in our arsenal. Minor inconsistencies in programming can lead to major watering inefficiencies. Incorrect adjustments in the field that are not corrected in the computer can also contribute to poor use of water. There is no doubt, each year we are close on the amount of water needed to maintain the turf and the amount of water in our storage lakes, but with the efforts made over the past three years, we have lessened the our historic water shortages.
Water is our most precious resource. Making sure to apply it in the most efficient way is important to the sustainability of our club. Superintendents still make use of time interval irrigation, but calculating the actual plant water use and replenishing that water, is the most accurate application method available today. When you are out on the course enjoying the summer weather, you can appreciate the science behind the way we use our water.If you have any questions about ET or how we apply water to the golf course please feel free to contact me.
Justin C. Ruiz, CGCS
jruiz@therimgolfclub.org
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