2020年鄱阳湖单退圩分洪效果及其方案优选

Effects of flood diversion and scheme selection of Lake Poyang semi-restoration polder in 2020

单退圩是鄱阳湖防洪体系的重要组成部分,能否将其科学运用直接影响着湖滨地区的防洪安全与蓄滞洪区的运行管理。2020年鄱阳湖单退圩首次全面启用,本文结合实际情况系统模拟了圩堤分洪过程并分析分洪效果,进一步运用模糊优选方法从降低水位、启用频率和年均损失等方面筛选启用方案,最后讨论单退圩体制机制及运行管理存在的问题。结果表明,2020年鄱阳湖单退圩累积分洪量为24.7亿m^(3),24 h降低水位最大达0.236 m,分洪时段集中在7月8日至17日,启用分洪48 h圩堤总分洪量占总分洪容量的40.3%,圩堤分洪效率有待进一步提高。单退圩启用与洪水过程存在一定关系,根据保护面积设置圩堤启用方案,湖口水位21.50 m(保护面积万亩以下,1万亩=6.67 km^(2))和21.68 m(保护面积万亩以上)为优选方案对应的水位,相应地分洪48 h最大降低水位、启用频率和年均损失分别为0.621 m、9.80%和2.516亿元。单退圩相关法律法规不完善,管理体制机制不健全直接影响圩堤分洪能力,地方发展导致分洪容量减少约2.0亿m^(3),且大部分圩堤分洪设施不能满足分洪效率要求。为了提升鄱阳湖单退圩的分洪能力,有效发挥其分洪缓冲作用,建议根据实际情况统一调整圩堤系统的分洪布局,同时建立协同运行调度决策机制,以应对未来鄱阳湖可能遭受的超标准洪水。

The semi-restoration polder is a significant aspect of the flood control system of Lake Poyang,and the scientific application of the semi-restoration polder directly impacts the flood control safety and management of the flood detention areas in the lake.The Lake Poyang semi-restoration polder was fully implemented for the first time in 2020.In this paper,the flood diversion process,as well as its effect on the polder,was first simulated and analyzed based on the actual 2020 flood.Moreover,the fuzzy optimization method was used to develop the optimal operation scheme on the basis of three aspects—water depth reduction,application frequency,and average annual loss.Finally,problems existing in the institutional mechanism and operation management of the semi-restoration polder were discussed.According to the results,in 2020,the flood diversion process in Lake Poyang was concentrated from July 8 to 17—with the cumulative flood diversion at 24.7 billion m^(3)and the maximum^(2)4-h reduction in water depth at 0.236 m.Additionally,as the total 48-h flood diversion accounted for 40.3%of the polder's total flood diversion capacity,the flood diversion efficiency needed to be further improved.In fact,a relationship existed between the optimal operation scheme and the lake flood process.The diversion levels of the optimal scheme of Hukou Station were 21.50 m(when the protected area was<6.67 km^(2))and 21.68 m(when the protected area was>6.67 km^(2)),while the corresponding 48-h maximum reduction in water depth,application frequency,and average annual loss were 0.621 m,9.80%,and 251.6 million yuan,respectively.The results also revealed a number of problems,such as capacity reduction of about 200 million m^(3)due to local development,legal and regulatory deficiencies,and issues related to the management of the semi-restoration polder.Moreover,most of the polder inlet facilities failed to meet the efficiency standards of flood diversion.To improve the flood diversion capacity of the Lake Poyang semi-restoration polder and the flood diversion buffer in the flood detention area,the polder's flood diversion layout should be dynamically modified according to the actual situation and establish a collaborative decision-making mechanism to deal with possible over-standard floods in the future.