Analysis Of The Influence Of Large Hydraulic Project On The Yangtze Estuary's Ecological Environment

The influence of large hydraulic project on the estuary's ecological environment is the research topic to the realm of environment and ecology at present. This paper adopts some technic means on the basic of the actual condition of the Yangtze Estuary's ecological environment, such as theoretical analysis, consultation of the expert, observation and investiage on the scene ect, and analyses the cumulated influence of water ecological environment systematically on the large hydraulic project, such as Three Gorges Project, South-To-North Water Diversion and Diversion From the Yangtze River To the Taihu Lake for the first time.Fist of all, this paper analyses the cumulated influence of Three Gorges Project, South-To-North Water Diversion and Diversion From the Yangtze River To the Taihu Lake on the Yangtze Estuary's runoff, and takes the representative year (low flow year, median flow year and high flow year) that Three Gorges Project designed as the standard, then computes the value of runoff by each distribute means. The result shows that the value of runoff is the most change in October, the reduced percent of low flow year, median flow year and high flow year are 41.3%, 23.8% and 19.8% respectively; the reduced percent is more obvious in November of low flow year to 27.3%; the value of runoff are relevant increase in February of low flow year and March of low flow year, but the increased percent isn't very obvious, the range are between 1.9% and 6.2%; the Yangtze Estuary's runoff is only influenced by South-To-North Water Diversion and Diversion From the Yangtze River To the Taihu Lake from June to September, the value of runoff are relevant reduction, but they are in flood season, the reduced percent isn't too obvious.Secondly, this paper analyses the cumulated influence of the large hydraulic project on the Yangtze Estuary's water quality, includes brine inbreak and the change of other parameter. This paper analyses the actual condition of the Yangtze Estuary's water quality detailedly, then analyses the cumulated effect on large hydraulic project by the actual condition of water quality, the result indicates that brine inbreak turns worse and the diluent ability of water body also becomes weak as the runoff is reduced, the reduced runoff enlarged the polluted degree of water body when the discharge of sewage is invariable and results in futher depravation of water quality.Finally, this paper discusses the cumulated influence of the large hydraulic project on biological diversity. The Yangtze Estuary's Water biological diversity mainly includes phytoplankton, zooplankton, zoobenthos and fish. According to their respective characteristics, live temperament, the place of lay eggs and propagale, migration and influence each other between biological diversity and the runoff, this paper can analyse the cumulated influence of the large hydraulic project on biological diversity. The reduced proportion of phytoplankton and zooplankton is 65.9% and 64.1% in October of low flow year respectively; the main influence is amount and distribution of zoobenthos, the amount is more increased than the nature after the runoff is reduced, the distribution of freshwater species moves towards the Yangtze Estuary; the influence is more complicated on fish resources, this paper mainly analyses migratory fish and the result is that their migratory route, the place of propagate and inhabit takes place a change probably after migratory fish is influenced by large hydraulic project.