A Simulation-Optimization Model for Conjunctive Use of Canal and Pond in Irrigating Paddy Fields

In this study, a new methodology is presented for conjunctive use of canal and pond to assess the role of ponds in saving local water and optimizing use of them in supplying irrigation water requirement of paddy fields. Evapotranspiration, runoff, irrigation water requirement, irrigation interval and pond water balance were simulated and then number of canal intake, storage volume and released volume of pond were optimized by binary genetic algorithm. Minimizing the number of canal intake and limitations of no deficit irrigation and storage volume of pond was defined as objective function and constraints, respectively. The effectiveness of the proposed methodology is examined through applying it for Fashtam pond in Sangar, Guilan province in Northern part of Iran. The results showed that 60, 54 and 46% of irrigation requirement of paddy fields were supplied by precipitation and runoff water saved in Fashtam pond and the rate of overflow of pond to maximum pond volume were 100, 74 and 34% in wet, normal and dry years, respectively. The model develops a scenario to increase pond capacity in selected case study for Fashtam pond located in Guilan province in Iran. It demonstrates how supply of irrigation to paddy fields has been increased to 100, 91 and 61% in wet, normal and dry years, respectively through simulation-optimization approach.