Conflict between water demand and environmental flow requirements is a challenging aspect in the reservoir management. Hence, optimizing environmental flow regime is one of the most important tasks at downstream of the large dams. The present study proposes a coupled simulation–optimization method based on the wetted perimeter method as an assessment method of the environmental flow and optimization of the reservoir operation to minimize difference between habitat loss and water demand loss using different metaheuristic algorithms. Moreover, the fuzzy TOPSIS as the decision-making system was applied for ranking the optimization algorithms. Indices including reliability index, vulnerability index, root mean square error and mean absolute error were utilized as criteria to measure the system performance and to select the best algorithm. Based on the results, gravity search algorithm (GSA) was the best method to optimize environmental flow regime at downstream of the reservoir in the case study. The proposed method is able to optimize environmental flow to minimize conflicts between human’s needs and aquatic’s needs considering storage constraints in the reservoir management. The proposed method might minimize negotiations between environmental managers and stakeholders. Furthermore, it should be noted that original wetted perimeter method is not able to provide optimal environmental flow regime based on a balance between users and constraints in the reservoir management such as storage constraints. The proposed method converts wetted perimeter method from an assessment method to a simulation–optimization method for optimizing environmental flow at downstream of the reservoirs.

水需求和环境流量需求之间的冲突是水库管理中的一个具有挑战性的方面。因此，优化环境流态是大坝下游最重要的任务之一。本研究提出了一种基于湿周法的耦合模拟-优化方法作为环境流量的评估方法和水库运行的优化，以使用不同的元启发式算法最小化栖息地损失和需水量损失之间的差异。此外，模糊TOPSIS作为决策系统被应用于对优化算法进行排序。以可靠性指标、脆弱性指标、均方根误差和平均绝对误差等指标作为衡量系统性能和选择最佳算法的标准。基于结果，重力搜索算法（GSA）是在案例研究中优化水库下游环境流态的最佳方法。考虑到水库管理中的存储限制，所提出的方法能够优化环境流量，以最大限度地减少人类需求和水生需求之间的冲突。提议的方法可能会尽量减少环境管理者和利益相关者之间的谈判。此外，应该注意的是，原始湿周方法不能基于用户和水库管理中的约束（例如存储约束）之间的平衡来提供最佳环境流态。所提出的方法将湿周方法从评估方法转变为优化水库下游环境流动的模拟优化方法。