耦合营养负荷的查干湖全季节适宜生态水位阈值研究

The threshold value of all-seasons suitable ecological water level coupled with nutrient load in Lake Chagan

适宜生态水位作为反应湖泊水文情势的重要指标,是维持湖泊生态系统稳定的关键要素。已有研究大多集中于水文过程对生态系统影响,缺乏耦合考虑湖泊营养负荷的全季节生态水位阈值研究。本研究在刻画恢复天然水位情势的基础上,综合考虑了人类活动导致湖泊营养负荷的季节性波动以及冰封期的最小生态水位,构建了适用于季节性冰封湖泊全季节的适宜生态水位阈值获取的综合框架,确定了年内不同时期适宜生态水位阈值。结果表明,查干湖入湖口非冰封期的总氮(TN)浓度与平均水位均呈上升趋势,总磷(TP)浓度呈下降趋势;6月湖内TN和TP滞留量最高,分别达到1044.36和23.61 t;确定了查干湖全季节不同时期的适宜生态水位,冰封期(11月—次年4月)为129m,汛期(6—9月)为130.15~130.86 m,非汛期(5和10月)为130.08~130.57 m。研究结果可为季节性冰封湖泊的适宜生态水位研究提供方法支撑,也可为湖泊的水环境管理提供理论支撑。

The suitable ecological water level is a key element to maintain the stability of lake ecosystems,as well as an important indicator reflecting the hydrological situation of lakes.Most studies of suitable ecological water level focused on the hydrological processes.There was lack of research on all-season ecological water level thresholds coupled with lake nutrient loads.On the basis of depicting the restored natural water level,a comprehensive framework for the suitable ecological water level calculation was built with consideration of lake nutrient load caused by human activities and minimum ecological water level during ice-covered period.The suitable ecological water level thresholds at different periods were determined in our study.The results showed that both total nitrogen(TN)concentration and water level of the rivers entering the lake in the non-freezing period of Lake Chagan had an upward trend;the total phosphorus(TP)concentration showed a downward trend;the maximum retention of total nitrogen and total phosphorus in the lake reached 1044.36 t and 23.61 t in June;the suitable ecological water level was 129 m in the ice-covered period(from November to next year April),130.15-130.86 m in the flood season(from June to September),and 130.08-130.57 m in the non-flood season(May and October)respectively.The results can provide method support for the study of the suitable ecological water level of lakes with seasonal ice cover,and provide theoretical support for the water environment management of lakes.