洱海水动力特性与入湖污染物迁移扩散规律研究

Study on the hydrodynamic characteristics and transporation and diffusion of pollutants in Erhai Lake

洱海是大理白族人民的母亲湖,具有浅水湖泊的水流特点。受风生湖流形态、环流结构及其空间分布差异性影响,洱海入湖污染物呈现水力停留时间长、输移扩散缓慢、北部湖湾藻类易出现富集等特点,并在自北向南、自西向东输移扩散过程中不断向湖底累积并形成内源污染,同时洱海水质受雨季降雨径流携带大量点面源负荷入湖及湖泊拦蓄雨季雨污水影响显著,从而形成目前洱海湖区水质北部高-中间低-南部稍高、西边高-东边略低及雨季水质快速变差的时空分布格局,因此加强流域面源污染治理、减少高浓度初期雨污水入湖,并尽快实施外流域引水以改变目前洱海因水资源短缺形势下的“蓄浑排清”调度运行方式,是近期快速推进洱海整体水质达标并减缓雨季水质快速变差的关键所在。

The Erhai Lake,the second largest freshwater lake on the Yunnan Platea,is a shallow-water Lake.Wind is the major driver of water flow while impact of its inflow and outflow is relatively weak.The water flow is complicated anddriven by wind and the inflow and outflow,varying between 1.1cm/s and 2.0cm/s.As a result,the pollutant of the lake is characterized by a long residence time,slow transporta⁃tion and diffusion,and algae is easily accumulated in the northern bay of the Erhai Lake.When the in⁃flow pollutants move from north to south and from west to east,they accumulate in the bottom of the lake and form the internal pollutions.Meanwhile,a large amount of the non-point pollutant load flows into the lake during the rainy season.As a result,the pollutant concentration is highest in the north and west,less in the south and east,and lowest in the middle,and the water quality is quickly degraded from June to October.Therefore,measures,such as controlling the non-point source,decreasing the water flowing the lake during the wet season,supplying water from other basin,and changing the present operation scheme,are the key ways to solve the water quality problem and to prevent the water quality from rapid degradation during the rainy season in the Erhai Lake.