Landscape Irrigation Systems

Abstract

As with turf irrigation, the goal of landscape irrigation is aesthetic. Plants (trees, shrubs, groundcover, and flowers) can be irrigated to just survive or to thrive, to maintain plant biomass or to have vegetative growth. Research on landscape plant water requirements has been limited, and many systems are not adjusted to match seasonal changes or changes in plant canopy area. The largest water user in many cities is irrigation so improved irrigation management is critically important in water stressed regions. Although traditional landscape drip irrigation systems have proven to be unreliable, new systems are more reliable: multiport emitters mounted on PVC pipe, inline drip irrigation tubing, and bubbler irrigation systems. Another key to successful system performance is the proper design and installation of the control zone. The typical control zone has a ball valve, solenoid valve, filter, and pressure regulator installed in a valve box. This chapter focuses on the installation methods and components in landscape irrigation systems.

Questions

• 1. Discuss the questions presented in Exercise 15.1. How would the scientific method change the results and people’s perceptions? (Write at least 1 page, double-spaced).

  Answers will vary.

• 2. Describe the components in a landscape irrigation control zone and the function of each part.

• 3. Describe how a controller is wired and how it controls the valves.

• 4. Compare the advantages and disadvantages of barbed fitting emitters, line source drip irrigation and bubbler irrigation.

• 5. Describe how a pressure compensating in-line emitter works.

• 6. Answer in-class Exercise 15.2. Using Table 15.2, determine the maximum distance between 4 LPH emitters in order to create a line source wetting pattern in a sandy soil? Would you select 30, 45, or 60 cm spacing?

• 7. Draw out a yard that you know about or can imagine and lay out the location of sprinklers and drip emitters. You can do this on a piece of graph paper where 1 inch = 10 ft or some other appropriate scale. You could also draw it out in a computer program. Locate positions of valves and pipes as well as define zones. For bubblers, let flow rate be 2 GPM, and for emitters let flow rate be 2 GPH. Use PVC or polyethylene tubing where appropriate. Make sure to group similar emitters in zones. Select pipe and calculate pipe friction losses.

• 8. Evaluate the economic costs and benefits of the following system. Assume 8 % ROR and 8 year project life.

  • Water costs for irrigation are $500/yr

  • Capital cost for installation is $1,500

  • Home selling price is $200,000 and landscaping adds 17 % to the value of home. Home will be sold in 8 years and home price is expected to decrease in value by 10 % over the 8 year period.

  • Irrigation system maintenance are $250/yr

  • Plant replacement costs are $100/yr

• 9. Which types of irrigation devices would be appropriate for four 5 m diameter, widely spaced, trees?

• 10. Which types of irrigation devices would be appropriate for 10 x 50 ft planter with ground cover?

• 11. If you had an oleander hedge that extended for 200 ft, which type of irrigation system would be most appropriate and why?

• 12. If you had six 1.2 m diameter shrubs that are spaced at 3 m interval, which type of irrigation system would be most appropriate and why?

• 13. Calculate the flow rate of the Toro Bubbler with three turns at 140 and 210 kPa.

• 14. Find the length of coiled tubing required to wet ½ of the canopy area of a 10 m diameter orange tree. Soil is clay, and emitter flow rates are 3 LPH. The tree trunk is 0.3 m diameter. Determine the cost of tubing per tree if the inline tubing costs $0.76/m.

• 15. For the parameters in question 14, find the fraction of canopy area wetted with a 12 m length of tubing.