Bubbler irrigation for urban desert landscapes with water harvesting

摘要

The goals of this research were to evaluate screw-adjustable and rotating cap bubblers for uniformity, to develop equations and a simple spreadsheet that can be used by landscape designers and managers to adjust bubblers to match the water requirements of individual trees and shrubs, and to evaluate the error associated with bubbler adjustment with the equations. Five brands of bubblers were evaluated for manufacturing variability at the fully open position with volumetric flow measurements. Coefficient of variation ranged from 8 percent to 21 percent. A study of bubbler flow rate vs. the number of screw turns or cap turns and vs. pressure (140 and 210 kPa) was conducted at the University of Arizona Campus Agricultural Center Irrigation Laboratory. Second order polynomial equations were derived by regression that modeled the flow vs. screw turns curves. The next step was to calculate k and x (q = kH~x) at each screw turn position based on the fitted equations for bubbler flow rate vs. the numberof screw turns. The accuracy of the equations for k and x was evaluated by calculating the average difference in calculated flow rate and measured flow rate vs. screw turns curves at 140 kPa. Average differences ranged from 0.1-lpm to 1.11-lpm for the 5bubblers. For flows calculated with k and x values calculated from the original flow curves, average differences ranged from 0.05- to 0.41-lpm. An Excel spreadsheet was set up to calculate the number of screw turns for each bubbler and the watering timeand length between watering times in a variable tree size irrigation zone. For a zone with orange trees of 3.0, 2.7, 2.1, and 2.1 m diameter, the number of 360 degree screw turns for a Hunter bubbler was 1.25, 0.81, 0.4, and 0.4, respectively. Finally,a method of soil contouring that combines bubbler irrigation with water harvesting was discussed.