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Years ago, as a landscape contractor, I met with the irrigation Foreman at a job site. There was a spot in the yard with dying grass. I told him it looked like the sprinklers were not getting the area wet. He told me to stand in the dry spot, he would turn the sprinklers on to see if I got wet. Not the best science and a poor excuse for a problem with the sprinklers. As you can imagine, water was shooting over the dry spot and not landing in the area with dead grass. I should have brought my tuna cans to show him the problem.
When you do your tuna can test you will be surprised to see the difference in the amount of water in the tuna cans when the test is over. No, sprinklers are not perfect; they do distribute water with perfect evenness or uniformity. Good sprinklers, with the right nozzle, properly positioned will get close, but never perfect.
There is good science and math to help you quantify distribution uniformity, but I am not going to get into that here. When you run a tuna can test you will see which cans do not have as much water and those that may be over flowing. At the risk of pointing out the obvious, those areas with too much water are being over watered; so water is being wasted. But the grass probably does not look very good in the areas where tuna cans had very little water. So what do you do about it?
I had the call again today, “How much should I water?” My response was ½” is a good target. Then she said, “I water 40 minutes, is that enough?” So we started talking about tuna cans. The lights came on. When the sprinklers run for a given amount of time, they apply water to the landscape. The application of water can be measured in inches and valve-run time is measured in minutes.
Irrigation professionals know that sprinklers apply water at different rates. The application rate, also called the precipitation rate is expressed as inches of water applied in an hour. For example, fixed spray sprinklers apply water any where from 1.50” to 2.00” of water per hour. Rotating sprinklers apply water much slower; anywhere from 0.35” to 1.00” per hour.
Let’s go back to the tuna can test. If, in 20 minutes your sprinklers put an average of ½” of water in the tuna can, what is the precipitation rate? Yes, this is a test question.
There are many things you can learn by putting tuna cans out on the lawn, and then running your sprinklers. Let’s start with Lesson #1, is pretty obvious; here you can see how much water your sprinklers put down. But where does it go? How far will it soak into the soil? That depends on the soil.
In the smart irrigation control world there are two schools of thought; 1) Replenish soil moisture on a measured evaporation schedule or 2) Managed Allowed Depletion (MAD), in other words, determine the rate of evaporation in the soil and water when the soil needs it.
Before we go any further let's remember a couple things. Water evaporates. There is experienced science that can accurately estimate how much water evaporates by measuring climate conditions. Although the sun is the biggest energy source in evaporation, water evaporates faster when its windy. and slower when the humidity is high. You have seen it; on long, hot, dry windy days plants dry out quickly. On cool, calm, cloudy days plants don't need much water.
You can buy smart phones, smart homes, and smart water. I am suggesting you water smart; let technology help you water your lawn. Smart technology relieves us of complicated problems. Water is a precious resource; too many times sprinkler timers are set and forgotten. You can save money and sustain healthy landscapes with climate controlled irrigation.
Fifty years ago my dad brought an IBM computer home from work and we played tic-tac-toe with a main frame computer in San Jose. Computers have come a long way since then. I love technology; it can do so many things faster and better than we can.
Then, in 1983 I was introduced to climate controlled irrigation; a weather station, connected to a PC controlled irrigation schedules. I was hooked. From that moment on much of my life's energy has been used to expand the use of smart irrigation control. Over the last 30 years in the irrigation industry I have seen great irrigation technology, toys and junk. I love the good stuff, it is fun to watch it do its job; when water gets used efficiently, people save money and landscapes look great.
There are two expressions I use from time to time; Water Smart & Water Right. My last blog post was about watering smart, so I’d better explain "Water Right." My wife was proof reading an article where I used the expression "Water Right," she crossed out "right" and changed it to "correctly." She teaches English at a USU, she should know and she is right, she is always right or should I say, she is correct. I told her I like the word right, it sounds better and rolls off your tongue easier.
So how does someone water right? (Or should I say, correctly?)