The Science of ET

We've had a lot of customers ask how our "smart" features work. Questions like: Where do the recommended watering times come from? Why did the Iro suggest those numbers? How does Water Budgeting know what my new watering times should be? The answer to all of those questions is the same: through the magic of ET.

ET and the Water Cycle

Evapotranspiration, or ET, is a measure of how much water a group of plants (like your lawn or trees) loses in a given period. It's basically the combination of how much water evaporates from the soil itself, and how much water the plant transpires, or "breathes out". (That's where the word comes from.)

ET is part of the water cycle, which describes how water falls to the ground as precipitation like rain or snow, is absorbed by plants and the soil itself and then returns to the clouds. Understanding the water cycle is important for climate scientists, meteorologists, and agricultural scientists, and lots of people spend their whole lives studying it. Fortunately, we're really just interested in how it works in one area: your yard!

ET and Your Yard

All of the science boils down to this: your yard gains moisture from precipitation, and loses moisture from ET. If you lose more than you gain, you get dry soil and brown foliage. That's what irrigation is for--but it's tricky. Irrigate too little, and you're just delaying your yard's demise. Irrigate too much, and you're wasting water, eroding your topsoil, and sending all kinds of junk into your storm drains (and thus our rivers and streams).

Figuring out just the right amount can be hard, and that's where ET comes in. A lot of smart people have researched how much ET occurs when you take all kinds of things into account: soil type, plant type, average temperatures, wind speed, humidity levels, latitude, average sun exposure, you name it. Figure out which equations to use, feed in the right variables, and you can decide exactly how much water your lawn needs in a given week. Know the watering rates of your sprinklers, and you can calculate just how long to water.

We Think Hard, So You Don't Have To

Fortunately, you don't have to be a climate scientist to figure it out. Our software uses your zone details, location, climate data, and weather to run the numbers and recommend the best watering schedule for your lawn. And, as conditions change, Water Budgeting changes your schedule to match. It's not perfect - there are a lot of different types of sprinklers out there, for example - but we're working every day to collect more data to make our system smarter. We're not going to be happy until everybody has a great yard, that never wastes a drop of water!