- Author: Greg Overduin
Last week, the UC Cooperative Extension, the Department of Water Resources, local water districts, Ewing Irrigation and many other partners held the "Get Ahead or Get Parched" workshop at the Irvine Civic Center. The purpose was to familiarize landscape professionals in Orange County and the surrounding areas with best practices in conserving water, especially the water lost through preventable run-off.
Jim Borneman, from Ewing Irrigation, presented for the lion's share of the day. He outlined a simple, easy-to-follow approach to using less water while irrigating professional landscapes. The foundation of the concept was simple: match the precipitation rate of your irrigation method to the infiltration rate of the soil. If your precipitation rate is higher than the infiltration rate, you get runoff. Runoff means lost water and lost profits - almost literally money down the drain.
These sprinkler precipitation rates, by the way, are easily accessible from the catalog supplied by the manufacturer. It will show the precip in inches per hour based off a certain GPM, radius, PSI and layout. As long as your irrigation meets the recommended configuration outlined by the manufacturer, you can easily find your precip rate and apply it to your soil type. This is an excellent reason to carefully check and maintain your irrigation system to keep it up to spec. If your PSI or GPM is too low or too high, you're losing money.
Jim gave an example of a clay soil with an infiltration rate of 0.1" per hour and a spray sprinkler with a precipitation rate of 1.6" per hour. Based on these numbers, the maximum runtime before runoff occurs is four minutes. It's not unusual to walk by sites in clay soil where they keep their sprinklers on for ten, fifteen or twenty minutes, with water running off into the gutter.
Obviously, you can't keep your plants alive by just watering them for four minutes a day. Every plant takes up a certain amount of water during the day to provide for its biological functions. The amount of water used is determined by the species as well as the weather and soil conditions. These environmental factors (wind, temperature, humidity, solar radiation, etc.) are used to determine the evapotranspiration, or "ET". The important part is that irrigators use the ET multiplied by a "crop coefficient" (K) to give them the amount of water that a particular species has used on a particular day.
The ET data is freely available online thanks to the CIMIS project from the California Department of Water Resources. They placed 145 automated weather stations all over the state that measure the surrounding environmental factors and spit out the current ET at an hourly rate. We have one of these stations here at the South Coast REC that is widely used across the county. If you don't happen to live close to a research station or agricultural college, you can make good assumptions based off the station closest to you. But for this example, we'll use the Irvine station.
I ran a report asking for a "Monthly Avg Eto" for the Irvine station (#75) and received this data. This is the average ET for each month based off the previous years (since 1987, I believe, when the station came online). Obviously, in a dry year like we're in, the average will be higher than this, but for our purposes we'll use this.
In landscaping, the traditional crop coefficient (K) is 0.7. This number is based largely on cold season turfgrass. Jim suggests using a lower coefficient of 0.6 in a drought year to conserve water but still keep the grass alive. So the formula for how much water that needs to be replaced in an average landscape uses in an average August is:
Then, to break this down into days:
That means, if you're watering every three days, you will need to replace 0.3576" of water (0.1192" * 3) each time you irrigate. If we go back to the example of the clay soil with a 0.1" infiltration rate we can figure out how many cycles we need to program for the sprinkler. We take the amount of water we need to replace (0.3576") and divide by the infiltration rate of the soil (0.1") to ensure we don't have any runoff.
The final step is finding the total runtime for the irrigation. Jim uses the following formula:
Where ET_L is the water we need to replace, PR is the precipitation rate of the sprinkler and 60 is a constant. So, we get:
We can round this up to 14, then divide by the number of cycles we need to prevent runoff like so:
Voila! All you need are four cycles of three and a half minutes each every three days for a great looking lawn with no runoff. The only numbers you need are your monthly average ETo (from the CIMIS website), the precipitation rate of your sprinklers (from the catalog) and the infiltration rate of your soil (find your soil from the USGS website and use a table like this one for the infiltration rate). Plug those numbers into these simple formulas and you'll be doing water wise irrigation in no time!
Dr. Akif Eskalen, University of California – Riverside, and Dr. John Kabashima, University of California Cooperative Extension – Orange County, gave a demonstration of the symptoms caused by the Polyphagous Shot Hole Borer (also known as the PSHB) today at the Huntington Library. In attendance were employees of the city of Pasadena and the California Avocado Commission, as well as Dan Berry, the nursery manager of the Huntington's botanical gardens, and Dr. Sabrina Drill, University of California Cooperative Extension – Los Angeles.
For more information about Fusarium dieback and the PSHB, check out the Eskalen Lab at UCR.
For handouts in English and Spanish regarding the symptoms and what to do if you find them, click here.
If you suspect that you have found this beetle or seen symptoms of the Fusarium dieback on your tree please contact either the County Ag Commissioner office, your local UC Cooperative Extension farm or pest control advisor, or Dr. Akif Eskalen.
The drought is here, it's hot and you don't want your plants to wither away, let alone have to pay higher water bills - what can you do? Among the many useful resources on the internet, you really should check out the Overwater Is Out page.
Sponsored by the OC Stormwater Program, this website has valuable information to help you save $$$ money on your water bill, reduce landscape water runoff, and improve the quality of your local watershed.
You will find landscape tips regarding the importance of mulching your garden to aerating your lawn, current irrigation and rain barrel product rebate information, an event calendar, plant recommendations through the OC Garden Friendly site, along with news and updates regarding local water issues.
Don't miss out on this valuable resource, visit http://www.overwateringisout.org/ today to minimize the impact of the drought to your wallet and your landscape!
Check out this message on the drought: http://www.youtube.com/watch?v=rQgyCjFeXdg&feature=youtu.be
Join the University of California Cooperative Extension on May 8th for three statewide science projects in honor of the 100 year anniversary celebrating a day science and service. Participants of all ages are asked to make observations and collect data that will be entered into a simple survey on any one of the three topics: pollinators, water, and food. Visit http://100.ucanr.edu/Day_of_Science_and_Service/ to learn how you too, can be a scientist for a day.