An irrigation system audit helps grounds managers better understand system performance compared to design intent. The Irrigation Association developed these guidelines as recommendations in auditing of irrigation systems. They are designed to aid managers and irrigation professionals in fieldwork procedures, techniques and performance calculations. Recommendations and projections from the guidelines and their accuracy depend upon the quality of measurements and data provided by an individual user. The association makes no warranty, implied or expressed, as to the results obtained from these procedures.
The irrigation system should be in optimal working condition prior to performing a test. Managers should verify that the irrigation system complies with local codes, identify operational defects or deficiencies, and assure that corrections have been made.
The guidelines for minimum catchment-device spacing are as follows:
The volume in milliliters (ml) should be approximately 11⁄2 times the throat area of the catch device in square inches. For example, if the throat area of the catch device is 20 square inches, the average volume of water should be 30 ml — 20 x 1.5 = 30 ml.
Linking, or using information from one station or zone and applying to another, may be used when there are a large number of sprinkler zones that are identical — the same sprinkler head, nozzle, spacing, operating pressure, and irrigating similar soil and plant types. The auditor may elect to perform catch device tests on one-third to one-half of the sprinkler zones to get an average value that could be applied to all sprinkler zones that are identical.
Workers should document and record the following data: sprinkler head locations; sprinkler head spacing; sprinkler make, model and nozzle size; approximate catch device locations; catchment readings; test run time; meter readings, if available; pressure readings with locations; wind speed readings; soil types and root zone depths; date and time of testing.
To calculate the precipitation rate using milliliter readings, use this formula:
— Irrigation Association
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Sidebar: Irrigation Audit Guidelines