Sec 6 The Irrigation Audit

The Irrigation Audit An audit is done on an irrigation system to help improve the system's performance. An audit will identify problems with water distribution in the system and provide information for scheduling. “Audits must provide consistent information that is practical, repeatable, and defendable. “ Before performing an audit the goals of the audit should be clearly defined. An audit can identify areas where the system needs adjustment in order to save water. It can identify how to eliminate wet spots and dry spots, how to prevent runoff and reduce water going below the root zone into groundwater. This in turn will save money. An efficient irrigation system will have healthier plant material and therefore a need for less fertilizer and chemicals. The Steps of a Landscape Irrigation Performance Audit are: 1. System and Site Inspection An auditor gathers data. It is not the auditor’s job to repair the system or redesign the system but if there are obvious flaws like broken pipe or heads then the auditor should make recommendations for repairs and postpone the audit until the repairs are made. Site data required for an irrigation audit includes soil information, root zone depth, plant information, wind speed, equipment manufacturing information and controller settings as well as sprinkler performance. 2. System tune-up “Any repair that involves putting a shovel in the ground is beyond tune-up.” (C.Boreland Irrigation Association Trainer)It is best to do the audit as close as possible to the condition the irrigation system has been running at, in order to point out where efficiencies can be made rather than fix the system first. 3. System testing An irrigation system is tested using a series of catch cans set out to catch and record water distributed by the sprinklers. The catch cans are set out in a grid which makes it easy for the auditor to identify areas where there is not enough or too much water being distributed. 4. Sprinkler Performance Calculations Data from an audit can be used to calculate distribution uniformity as well as net precipitation rates. This information is then used in scheduling an irrigation system. 5. Report of Findings Recommendations should be made to the homeowner or building manager as to improvements to the system. This list is taken from the Landscape Irrigation Auditor Manual 3rd Edition Irrigation Association Fairfax VA Feb 2013 To set up a simple audit Audits should be conducted as close to the same conditions as when the system will be running.Wind speeds should not exceed 5 mph (8kph) set up catch cans in a grid system in the area to be audited. The catch cans need to be uniform in size and shape. catch cans should be placed 30-60 cm from the edges catch cans should be placed within 2-3 feet from a head the second row should be a ¼ to a ⅓ of the sprinklers radius away from the first row. there should be a minimum of 24 catch cans in an area run the system 3-6 minutes for spray heads, 10-15 minutes for rotors The volume in ml should be 1.5x the throat area of the catch can in square inches. eg: 20 sq in x 1.5 = 30 ml Using a pitot tube or pressure gauge for spray heads take the pressure at the head in 2 locations in the test area. calculate distribution uniformity record the average volume of all the catch cans take the lowest quarter and record the average volume of those catch cans. Eg: if you set out 24 catch cans, record the 6 catch cans with the lowest volume of water. DUlq = average of lower quarter average of total volume Calculate net precipitation rate PR = 3.66 x V avg V = average volume tR x A CDt = test run time A= area of catch device When recording data use a spreadsheet and/or a diagram to indicate where the heads are where the catch devices are water collected at each catch device