Coupled model for optimizing the water distribution and gate control of the canal system in an irrigation district

Irrigation district canal systems deliver water to fields timely and adequately via check gates, with gate operation timings critical for service quality and operational efficiency. This study develops a coupled optimization model integrating a Linear-Quadratic Regulator (LQR) for precise canal water level control and a rotational irrigation grouping model to reduce energy consumption and equipment wear from frequent gate adjustments. The model was validated on a main canal section of a large-scale irrigation district in China, which was divided into three canal pools by four check gates. Three typical scheduling modes were implemented, namely top-down distribution, bottom-up distribution, and flexible distribution. Compared with the traditional Proportional-Integral (PI) control algorithm, the proposed method can significantly reduce both canal water level deviations and gate adjustment frequency. Taking Pool 2 as an example, the deviation reduction rate reaches 68 %-71 % during its key operational stages. Among the three scheduling modes, the flexible distribution mode achieves the shortest total operation duration of 244.85 h—compared with 259.8 h for the top-down distribution mode and 285.36 h for the bottom-up distribution mode—while simultaneously ensuring a higher water demand satisfaction rate. However, it may cause management inconvenience when canals with a long distance between upstream and downstream are grouped into the same rotation irrigation group. In contrast, the other two are easier to management but involve more frequent adjustments. This coupled model provides a novel technical approach for irrigation district water distribution and gate control, with important theoretical and practical value for improving water resource utilization efficiency and service quality.