Simple, Economical Measurement Method for Accurate Volumetric Water Accounting in Irrigation District Turnouts

Irrigation districts in California are required to provide volumetric water accounting for all customers. Fresno Irrigation District (FID) requested that ITRC examine the accuracy and feasibility of portable methods of measuring irrigation district turnout flow rates to meet volumetric water accounting requirements. The intent was to recommend a measurement method that provides accurate flow measurement while requiring minimal modification/cost for implementation with low head loss and a simple measurement technique. All components were located on the upstream side of a turnout to minimize modification. To determine the best method to accurately measure flow rate with a portable velocity meter on the upstream side of an irrigation district turnout, ITRC fabricated and tested multiple conditioning devices and tested various established velocity measurement methods. Initial iterations of the conditioning device were fabricated by ITRC, while the final device was commercially fabricated. All devices were tested at ITRC’s NIST-traceable testing facility. The final device was installed and tested for an irrigation season in FID. The final device (a cone-shaped conditioning device) was combined with a four-point velocity/area measurement and provided reasonable flow rate accuracy. However, ITRC has recommendations for improvement in future iterations.