湖泊水位变化对挺水植物影响分析:以洪泽湖为例

湖泊水位波动的幅度、频率、持续时长、规律性等是影响湖泊水生植被状况、水资源调配的关键因素。以往研究主要通过选取部分水位变化指标来识别主要的生态影响。而要维持湖泊生态健康进行合理水位调控，需要综合水位变化的多指标，从整体上分析湖泊植物对湖泊水位变化的响应特征。以洪泽湖为例，基于IHA/RVA法，重点分析了南水北调东线一期工程后洪泽湖水位变化对挺水植物的影响。结果表明:南水北调东线一期工程后洪泽湖3，5，7，9月月平均水位以及最小30 d平均水位等指标发生较大改变，对挺水植物面积的影响是最显著的，其他IHA指标改变度小，影响不明显。3月平均水位超过13.4 m，挺水植物萌发抑制明显；当5月平均水位在13.1 m，7月平均水位在12.7 m时，挺水植物面积显著增加；9月平均水位高于13.4 m，挺水植物面积大幅减少。当最小30 d平均水位<12.0 m时，挺水植物面积平均减少14.32 km2。为满足洪泽湖挺水植物生长和繁殖需求，确定3，5，7，9月适宜生态水位为13.20，13.10，12.70，12.85 m。

ANALYSIS OF EFFECT OF LAKE WATER LEVEL CHANGES ON EMERGENT PLANTS: A CASE STUDY IN THE HONGZE LAKE

The amplitude, frequency, duration, and regularity of lake water level fluctuations are the key factors affecting the status of lake aquatic vegetation and the allocation of water resources. Previous studies mainly identified the main ecological impacts by selecting some water level change indicators. To maintain the ecological health of lakes and carry out reasonable water level control, it is necessary to integrate multiple indicators of water level changes and analyze the response characteristics of lake plants to lake water level changes as a whole. Taking the Hongze Lake as an example, based on the IHA/RVA method, this paper focused on the analysis of the influence of the Hongze Lake water level changes on emergent plants after the first phase of the East Route of the South-to-North Water Diversion Project. The results showed that after the first phase of the East Route of the South-to-North Water Diversion Project, the Hongze Lake’s monthly average water level in March, May, July and September and the minimum 30-day average water level changed in height, which had the most significant impact on the area of emergent plants. For the other IHA indicators, the degree of change was small and the impact was not obvious. When the average water level in March exceeded 13.4 m, the germination of emergent plants was significantly inhibited; when the average water level in May was 13.1 m and the average water level in July was 12.7 m, the area of emergent plants increased significantly; when the average water level in September was higher than 13.4 m, the area of emergent plants was greatly reduced; when the minimum 30-day average water level was less than 12.0 m, the area of emergent plants decreased by 14.32 km2 on average. From the perspective of maintaining the area of emergent plants, and the reverse seasonal hydrological process of the Hongze Lake to meet the needs of the growth and reproduction of emergent plants, the suitable ecological water levels in March, May, July and September should be determined at 13.20 m, 13.10 m, 12.70 m and 12.85 m, respectively.