ET-based irrigation controllers? When you hear that you may think back to the early 80’s when E.T. was all the rage. But the ET I’m referring to has nothing to do with phoning home. ET stands for evapotranspiration. Evapotranspiration, as defined by the Irrigation Association, is the loss of water from the earth’s surface through the combined processes of evaporation from soil and plant surfaces, and plant transpiration. So what does all of this have to do with your irrigation system? Simply put…everything.
If you have an irrigation system in your garden you should be concerned with evapotranspiration. When you set your irrigation timer to water Monday, Wednesday and Friday for 30 minutes on each zone, your system will water the same whether the temperature is 70 or 90 degrees, whether there is a light breeze or 20 mph wind, whether the humidity is 40% or 90%. Unless you have a rain sensor on your system (which you should…they can be installed by a professional for less than $100), your system will water for 30 minutes if it rained 1/10″ or 2″ earlier in the day. What if you could have a controller that would take all of that into account and then water based on your plants’ needs. You can with an ET-based irrigation controller.
Hunter makes a very nice ET-based irrigation controller that I have personal experience with. Other irrigation manufacturers, including Toro, Rainbird and Irritrol, make ET-based irrigation controllers but I can’t speak to the quality of those controllers since I don’t have any experience with them. With the Hunter ET-based irrigation controller, you have your own weather station that records real-time data and converts all of that information so that your plants receive the water that they need. Here’s what it looks like:
It has a rain gauge, an anemometer that measures wind speed and a thermometer to determine the temperature at your specific site. When setting up the controller, you enter the following data that helps the computer determine when and how long to water:
- Soil type
- Crop being grown
- Age of crop (new vs. established)
- Sun exposure
This information is critical and the ET-based irrigation controller is only as good as the information that is entered at this stage. It is very handy to be able to enter different information for different zones according to their site conditions. Most landscapes have some sun and some shade, some turf and some landscape beds and some new plantings intermingled with the older ones. By entering and updating the information as conditions change, the controller is able to adjust the watering times and durations accordingly. Pretty cool huh?
So what does all of this cost? Well, that depends. If you already own an irrigation controller that is compatible with the ET-module, the cost is very reasonable…you can buy the module without the anemometer for the Hunter ET-based irrigation controller for $239.07 online. The anemometer is about the same price…so maybe you take baby steps in converting your existing system over….the choice is yours. While the upfront cost may turn you off initially, you should do the math to see how long the payback takes. Many localities are now charging a higher rate for water usage over a certain limit, aimed at users with irrigation systems. If you live in suburbia and have to pay sewer charges, the payback will likely take far less time unless you have a separate meter for your irrigation system. Also, consider the benefit of set-it-and-forget-it. No more adjusting your watering program when the temperatures soar to 95 degrees…the ET-based irrigation controller will adjust the watering times for you…yeah!
Of course, if you’re like me, my irrigation system is in the sky and it is completely at God’s will. If the rain doesn’t fall on my landscape, the plants don’t get watered. They’ll either live or die trying. My only exceptions to that rule are newly transplanted plants and vegetables. Since I don’t have a veggie garden at my house due to the abundance of shade, I don’t have that concern for now. Consider hugelkultur if you will be installing new beds in the future. It’s a way to garden without watering at all. That’s my kind of garden!
Let me know your thoughts about ET-based irrigation controllers…leave me a comment below or e-mail me at firstname.lastname@example.org. Happy gardening!