Several Sources of Nonuniformity in Irrigation Delivery Flows

Abstract

A lateral canal in a southwestern U.S. irrigation district was instrumented for continuous monitoring. Deliveries were flexibly scheduled; farmers arranged timing, rate, and duration with the district. The distribution of measured variables showed that the lateral was operated under a wide variety of demand and operational conditions and that farm delivery flows were frequently not uniform due to changing conditions along the lateral. Flows that are unpredictably variable affect the performance and evaluation of on‐farm application systems and, unless controlled, can negate the benefits of flexible scheduling (more precise management). Statistical analysis of 286 deliveries to nine farm turnouts indentified a number of sources of nonuniform flows which were a combination of canal hydraulics and operational characteristics. Time of year that deliveries occurred was shown to affect uniformity, as were median flow rate, delivery duration, and location of turnouts, both within a pool between two check structures and along the lateral. Identifying sources of nonuniformities is an important first step in devising structural and operational controls to improve delivery uniformity.