Spring into Scheduling - Part 1 of 3

By Lori Palmquist

Spring has burst upon us in its unstoppable wonder and glory. Even as we try to figure out how to navigate the losses and uncertainties this season has brought us this year, Nature is offering her bounty for us to adore.

Here in the Bay Area of Northern California, we’re a month into spring, and it’s about time to dust off those irrigation schedules and put them back to work.

I was asked by a survey respondent recently to cover how to translate how much water each plant in the landscape needs … into irrigation timer settings. I thought this would be the perfect time for a blog post (or three) since we’re nigh on the eve of the irrigation season in California. So, thanks for asking, Gail. These are for you!

Three Blog Posts

I divided this post about scheduling into three parts. The first part is scheduling in the simplest way I know. The second explains the scheduling formulas and shows how to use them. The third shows a web application that requires some technical knowledge of scheduling to use. Understanding of the concepts and formulas explained in part two will provide the expertise to use the web application in part three.

• Part One: Scheduling using web applications
• Part Two: Scheduling using formulas
• Part Three: Scheduling using a professional web tool

The Simple Answer to How Much Water?

Gail asked for a simple way to translate how much water each plant needs into irrigation timer settings. I’ll give the simple answer first, then explain in part two (a separate post) how to do it longhand. And in part three, I’ll offer up an app I created that I use for scheduling. It’s a combination of the first two parts, in that the app does the calculations in the background for you. But you do need to know what values to use in the formula the app uses.

The simplest way I know to create an irrigation schedule is to plug the logistical data into a calculator, and let it crunch the numbers and provide the answer in minutes of run-time per week. We schedule our irrigation controllers with weekly schedules, so minutes per week is the number we desire. I know of two web applications that will do this reliably and fairly quickly. I had a big hand in creating both apps, so I know them well.

The first one is the WhenToWater irrigation scheduler pictured here.

This web app currently lives at the following url:  http://whentowater.loripalmquist.com

This is a California-specific app. All you need to do is enter the address of the site. Then you tell the program the logistical data for each zone, such as exposure, water-use value of the zone, soil type, slope, wind, and irrigation type. You don’t need to know any numerical values. They're all assigned in the background. There’s even a drawing program within the app that lets you create a downloadable site map of the property that shows where the irrigation zones are located.

This app generates an irrigation schedule for every month of the year, based on historical weather data. You can either download a pdf of the schedule that’s generated or have it emailed to you, or both.

The second app is for folks who live in the Sacramento region of California. This web app is specific to El Dorado, Placer, Sacramento, and Yolo counties. It’s called the Sacramento Region Smart Irrigation Scheduler, and it can be found here:  http://beyondthedrought.com/.

It’s pictured below, and works basically the same as the app above that serves the whole state of California. The main difference between the functionality of this app, as compared to the WhenToWater app, is that it creates an irrigation schedule based on current weather (the past seven days). It will also create an irrigation schedule for every month of the year, based on historical weather data, like the WhenToWater app does.

Both of these web apps use a default value for the precipitation rate of drip, no matter what kind of drip is used. This is because the precipitation rate of drip has a wide range of possible rates. So, a reasonable “middle-of-the-road” value was chosen. This value is 0.8 inches per hour. This is a good starting place, and the schedule can be adjusted to suit, whether the plants are getting too much or too little water. If you’d like to know what precipitation rate is, I explain it in the second part of this post, in “Spring into Scheduling - Part 2 of 3.”

The Deeper Answer

You can certainly use the above two calculators to create your irrigation schedules. But if you’re intent on understanding the mechanics of irrigation scheduling and how schedules are created, read the second part of this post, my friend. Settle in with a nice cuppa joe or tea, and let’s get down to the nitty gritty.

Click here to read part two of this three-part series.