Optimization and Simulation of Drainage in Irrigation Districts Based on Coupling Model

The coupling model integrates drainage patterns with an objective function aimed at cost minimization using ditch depth and spacing as decision variables. Drainage constraints are applied to iteratively solve different combinations, ensuring compliance with drainage requirements while minimizing investment costs. The results show that there is little difference in drainage depth between the fixed and non‐fixed schemes and that both schemes can meet the requirements of paddy field drainage. The drainage project investment of the fixed ditch depth scheme is 8661 yuan·hm −2 . The non‐fixed ditch depth drainage scheme yields a value of 7808 yuan·hm −2 , representing a reduction of 10%. The drainage ditch depth is the same in the drainage optimization scheme with different drainage guarantee rates. Compared with the scheme with a 90% assurance rate, the drainage scheme with a 95% assurance rate results in a 4.2 m reduction in ditch spacing, accompanied by an additional investment of 720 yuan·hm −2 . The findings provide a scientifically grounded decision‐making framework for the cost‐effective design of farmland drainage systems, and engineering optimization can achieve a balance between investment costs and drainage performance, offering valuable insights for sustainable water management in agriculture.