Hi Everyone! I worked very closely with Emil at Rachio to help with my phx flex schedule and thought I’d share here. I don’t have grass, but am hopeful that his information helps others trying to set up their desert flex schedules. Just a note, my garden is brand new - shrubs planted in Feb 2016, so some of Emil’s suggestions refer to an establishment period. Those with well established gardens won’t need such high crop coefficients. Hope this helps.
****Emil writes: I’ve been working with Jeff Lee, who’s a Water Conservation in Gilbert. He’s testing the Rachio controller and was able to provide some insights into the issue we’ve been experiencing with desert watering. The biggest variable impacting the watering durations was the precip rate of the custom nozzle. Although the math indicates the values we were both using, he believes the value should be much lower on drip zones as they usually have a pressure regulator installed, which limits the water supply to the emitters. In his tests, he’s using a value of 0.4 in/hour for 2 GPH emitters; whereas as were using 3.2 in/hour. The best way to test this moving forward would be to use your water meter (if it’s accessible) and simply track the gallons reported before and after a zone runs. Since you’re watering your zones for long durations, I’d recommend running each zone for one hour and recording the number of gallons used per hour. This will allow us to quickly calculate the true water usage per zone. I edited a custom nozzle you weren’t using to 0.4 in/hour and it changed the watering duration of each zone to roughly 5 hours each @ 50% MAD (management allowed depletion), watering every 10-14 days.
** Additionally, in researching your plants, I believe we should edit the crop coefficients from 50% to 60% for this year, and reduce 10% per year for the next 2-3 years. Ideally, xeroscaped plants should have a crop coefficient of 30% +/- 10%.
** Moving forward, since your plants are young and establishing and have been use to getting water on a regular basis, I’d recommend we convert to a Flex Daily schedule with 10% to 20% MAD, and work to 50% MAD over the next few months, increasing 10% per month. As MAD increases, so does the watering interval and watering duration."