| This paper studied the current fishery water-environment situation at the downstream from Zhicheng to Jingzhou reach of the Yangtze River in 2002-2003 before and after the Three Gorges reservoir hold back. And had a investigation on the abnormal fishery environment after The ThreeGorges reservoir hold back. The primary results are as follows:1. The water-quality parameters exceeding the standard are TCu, TPb and TP at the monitor sites from Zhicheng to Jingzhou reach of the Yangtze River in 2002, and the rate exceeding the standard are 83.3%, 37.5% and 16.3% respectively. The parameters exceeding the standard are TCu, TPb , TP, UIA and oil in 2003, and the rate exceeding the standard are 3.6%, 6.7%, 31.8%, 30.0% and 100% respectively.2. The comprehensive water-quality index is 1.601 and 1.923 at Zhicheng and Jingzhou in 2002, While the comprehensive water-quality index is 0.868 and 0.806 in 2003. The water quality had the better trend from 2002 to 2003.3.The heavy metal and organic pollutions are major among the water pollution of the Yangtze River. The pollution degree in wet seasons is higher than that in normal and dry seasons.4. The Suspended paniculate matter concentration decreased roughly in downstream after the ThreeGorges reservoir hold back. The falling scale is from 43.45% to 89.66% than that in 2002. The average falling scale is 69.50% and 71.55% at Zhicheng and Jingzhou.5. The water temperature decreased 1.1 -1.2 in summer and autumn and increased 0.4-0.5 in winter after the ThreeGorges reservoir hold back.6. D.O concentration increases roughly in downstream because the Three Gorges reservoir releases water. The climax of D.O saturation is 130.2% and 118.6% at Zhicheng and Jingzhou.7. The surface water in the middle of the Yangtze River had strong biology toxicity to fish. It's the main reason that gas supersaturation has the character which the D.O concentration increases roughly. |
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