This is an article that appeared in the August 2009 Newsletter for SAWPA (Santa Ana Watershed Project Authority) written for them by Bryan Love, a project manager of DNA,Inc. Bryan is a graduate of Cal Poly Pomona in Landscape Architecture. He and his lovely wife Catarina live and work in Temecula while raising their two young boys Kaden and Grayson...
A standard practice for automatic irrigation systems for the past 30 years was to use rotor and spray head irrigation systems. When water was easily accessible and relatively inexpensive, the concern for wasting water didn’t play as large of a factor when designing the irrigation system. All that has changed with increasing water demand due to population increase and decreasing water supply due to consecutive years of drought. Water is a precious resource that cannot be wasted and regulatory agencies are introducing policies, restrictions and increasing rates to conserve our dwindling water supply. Counties across Southern California are implementing punitive and incentive programs to regulate the amount of water its residents can use to irrigate their yards.
Overhead spray and rotor irrigation systems play a large role in water waste. A typical spray head system is estimated to only be 70% efficient; meaning 30% of the water used is wasted due to wind, runoff and overspray on to impervious surfaces. For example, a 100 square foot area that has a typical spray head system, will waste 1.5 gallons of water per minute. If you water that area 6 days a week for 5 minutes, you would end up wasting 45 gallons of water per week and that is just 100 square feet. A typical single-family home has about 1,500 s.f. of lawn; so the amount of water wasted on a weekly basis is 675 gallons! So you can see that the inefficiency of the spray and rotor systems played a large role in water waste.
Fortunately, the irrigation manufactures and design professionals have been busy researching more efficient products and methods to water our landscapes. The Demonstration Garden at the Santa Ana Watershed Authority, (SAWPA) displays 3 different types of efficient irrigation systems.
Three of the landscaped areas in the garden use the Toro – DL2000 Drip line. This is a system that is generally installed on grade, under the mulch layer. The drip line comes with water emitters installed in the lines at either 12” or 18” on center. The drip lines are laid in a lineal pattern at 12”-18” on center, depending on the density of your plant material. When watering, the emitters on the drip line leak water which goes straight to the plants root ball and eliminates water runoff and overspray. The efficiency of the drip line is estimated by Toro to be 90-95% accurate. This method of irrigation is good for shrub planting areas that have a medium to high density of plant material.
Rain Bird Corporation’s– Xeri-Bug Emitters on Poly-Flex Risers is used to irrigate the Desert area in the demonstration garden. This system uses standard PVC pipe, installed underground, with two emitters installed on flexible risers going to each plant root ball. The Xeri-Bug Emitters slowly drip or “leak” water which eliminates runoff and overspray. The efficiency for this method of irrigation is estimated by Rainbird to be 90-95% accurate. A landscape design that has a low to medium density of plant material would benefit from this type of irrigation. Many of the landscapes in the desert area use this method of watering.
The vegetable garden is irrigated with Rain Bird Corporation – XPCN Micro Spray. This system uses either standard PVC pipe, or poly line tubing installed underground, with micro spray pop-up heads connected at 2’-4’ on center, depending on the radius of the spray nozzle used. This method of irrigation is good for small areas that have plant material that prefer overhead water. The water efficiency is estimated by Rainbird to be 85-90% accurate and would be a good application for vegetable gardens or small shade gardens.
Water is an important resource that cannot be wasted and fortunately there are irrigation products and designers that can not only help our cause in saving water, but also make our gardens grow beautifully and with vigor.
