基于沉水植物的太湖适宜生态水位研究

Suitable ecological water level of Lake Taihu

基于2000~2020年长系列监测数据,分析了太湖水文、水环境、水生态变化特征及相互关系.结果表明,2000~2020年太湖水位较1980~2000年抬升明显,2000年以来太湖水体总磷和叶绿素a浓度波动上升,沉水植物分布面积波动下降.长期来看,太湖水位对沉水植物分布面积具有一定影响,1~2月水位、3~4月水位、1~4月水位、5~7月水位、水位超过3.5m天数与当年5月沉水植物分布面积之间显著或极显著负相关,太湖年均水位、8~9月水位、水位超过3.5m天数与次年5月沉水植物面积之间显著负相关,水位对8月沉水植物面积的影响相对较弱.东西山之间水域、东茭咀水域是现阶段太湖沉水植物重点恢复区.结合沉水植物生活史,研究提出太湖适宜生态水位建立方法,建立的适宜生态水位具有较好的水文节律,且与太湖沉水植物水位需求吻合.沉水植物对太湖长期高水位具有一定的适应性,短期内正常的水位波动不会导致沉水植物分布面积剧烈降低,但受人工水草收割影响明显.降低水位是恢复太湖沉水植物的有效手段之一,但当前流域防洪、供水、水生态、水环境对太湖水位有不同需求,应在优化完善水草收割方案前提下,尽快建立太湖多目标统筹协调调度水位.

Water level is an important basic hydrological element,and its variation characteristics have an important impact on the structure and function of the lake ecosystem.Based on the long series of monitoring data from 2000 to 2020,the characteristics and correlation of hydrology,water environment and water ecology of Lake Taihu were analyzed.The results showed that the water level of Lake Taihu had risen since 2000,the concentration of total phosphorus and chlorophyll-a had risen fluctuated,and the distribution area of submerged plants had decreased obviously.The water levels from January to February,March to April,January to April,May to July and days over 3.5m were significantly negatively correlated with the distribution area of submerged plants in May of that year.The annual average water level,the water level from August to September and the number of days over 3.5m were significantly negatively correlated with the area of submerged plants in May of the next year.However,the influence of water level on the area of submerged plants in August was relatively weak when compared with May.The region between East and West Mountains of Lake Taihu and Dongjiaozui were potential key recovery areas for submerged plants.Based on the life history of submerged plants,the establishment method of suitable ecological water level of Lake Taihu was put forward for the first time,and the appropriate ecological water level was established.The appropriate ecological water level was more conducive to the germination and initial growth of submerged plants,and maintains a good hydrological rhythm.Due to the adaptability of submerged plants to long-term high water level in Lake Taihu,the fluctuation of water level in the short term would not lead to a drastic decrease in the distribution area of submerged plants.Artificial water grass harvesting was the main reason for the sudden decrease of submerged plant area in Lake Taihu in 2015.Reducing water level is one of the effective means to restore submerged plants in Lake Taihu,but flood control,water supply,water ecology and water environment in the basin all have different demands on the water level of Lake Taihu,so it is necessary to coordinate water security,water resources,water ecology and water environment,and to establish a multi-objective coordinated water level of Lake Taihu as soon as possible.