异龙湖水质时空演变特征及其驱动力分析

Analysis on spatial-temporal variation characteristics and driving forces of water quality in Yilong Lake

异龙湖是云南九大高原湖泊中流域面积最小、湖泊水量最少、水质污染程度相对最重、最易受人类活动干扰和近年来唯一干涸过的高原浅水型湖泊,受自然环境条件和人类活动双重驱动影响,近年来异龙湖水质演变过程十分复杂、水质污染问题日益突出。本文以湖泊水动力与水质模型为主要技术手段,并结合湖流原位观测,深入研究了异龙湖的水动力特性及入湖污染物的迁移扩散规律,初步揭示了异龙湖水质的时空演变特征及其成因。研究表明,水资源总量不足是影响异龙湖水质年际波动变化并逐步向封闭性湖泊转变的最主要因子,不利的湖流形态与不同特征污染物的来源组成是驱动异龙湖水质时空分布差异性的关键因素,随降雨径流输入的外源负荷、湖区浮游植物异常增殖合成的大量有机物和湖泊底泥释放的大量内源负荷是异龙湖2021年水质变差与快速返劣的重要驱动因素,因此,增加流域内清洁水资源量和入出湖水量、加快湖泊内源与陆域污染物输入治理、强化对雨季主要入湖河流水质浓度的管控,是实现近期湖区水质快速脱劣并持续性改善的关键。

The Yilong Lake is the smallest plateau shallow water lake of the nine major plateau lakes in Yunnan,which is the smallest in watershed area and water volume,the heaviest in water pollution level,the most susceptible to human activities,and the only one that has dried up in recent years.Driven by both natural environmental conditions and human activities,the water quality evolution process of the Yilong Lake has been very complex in recent years,and the problem of water pollution has become increasingly prominent.This paper uses the constructed lake hydrodynamic and water quality model as the main technical means,combined with in-situ observation of lake flow,to deeply study the hydrodynamic characteristics of the Yilong Lake and the migration and diffusion laws of pollutants entering the lake.It preliminarily reveals the spatiotemporal evolution characteristics and causes of water quality in the Yilong Lake.Among them,insufficient total water resources and inappropriate scheduling and operation management are the main factors affecting the inter-annual fluctuation of water quality in the Yilong Lake and resulting in gradually transitioning to a closed lake.The unfavorable lake flow pattern and the source composition of different characteristic pollutants are the most critical factors driving the spatiotemporal distribution differences of water quality in the Yilong Lake.The external factors from rainfall and runoff,the abnormal proliferation and synthesis of phytoplankton in the lake area,as well as the release of a large amount of endogenous loads from lake sediment,are important driving factors that cause the water quality to deteriorate and return rapidly to a worse level in the Yilong Lake in 2021.Therefore,increasing the amount of clean water resources and inflow and outflow in the basin,accelerating the treatment of endogenous and terrestrial pollutants in the lake,and strengthening the control of water quality concentration in the main rivers entering the lake during the rainy season are the key to rapidly getting rid of deteriorated water quality and realizing the continuous improvement of water quality in the lake area in the near future.