Assessment of the environment effects of constructing the Three Gorge Project on the Yangtze River
The Three Gorge Project is a multipurpose project with the primary function of flood control. Other functions include power and navigation and could include irrigation. A 200 m high concrete gravity dam, currently being considered, would be located in the lower reach of the famous Three Gorges of the Yangtze River in Hubei and Sichuan Provinces. The reservoir will store about 70 x 10 to the 9th cu m and extend upstream about 780 km. The proposed powerplant would have an installed capacity of 25,000 MW, consisting of twenty-five 1000-MW units. The Three Gorge Project, when constructed, would be the largest water resource project anywhere on earth. Beneficial effects include elimination of flooding along the middle and lower reaches of the Yangtze River, a substantial increase in much needed electric power for south and central China, and creation of a large body of water which could be used for aquaculture. Consideration is also being given to diverting water to the North China Plain, one of the most important agricultural areas of China. Major adverse impacts include relocation of more than 2 million people for the reservoir area; loss of habitat for many kinds of Yangtze River aquatic life, including themore » unique Chinese sturgeon; and the possibility of reducing nutrient input to the downstream and estuarine fisheries. The possibility of minimizing adverse effects seems high, if the potential environmental impacts are identified and means of mitigation are carried out. 22 references, 1 figure.« less
The World Bank's new environmental policy for dams and reservoirs.
Water development schemes are fraught with major environmental problems, especially in the tropics. However, where gains in conservation and use efficiency of energy and water have been substantial, then such schemes can often be more appropriate than alternatives, such as coal and nuclear. But this means that the environmental impacts of water development schemes must be prevented, mitigated or compensated for much more effectively than hitherto. The World Bank's new policy is designed to do just that.
7 - Orientation and Fish Migration
The life cycle and homing migrations of salmon are defined within three distinct phases: (1) A sojourn in the inland stream beginning with the fertilized egg, through at least the larval and early fry stages, terminating with a short downstream migration of fry of pink or chum salmon or with a long downstream migration of smolts of sockeye, coho, Chinook, or Atlantic salmon to the sea, ( 2 ) a period of rapid growth and far ranging movement in the open sea, concluding at sexual maturity with an extensive homing migration of several hundred kilometers to the mouth of the home–river system, and ( 3 ) a strenuous upstream drive over barriers and waterfalls with rejection of tributary after tributary until the stream of origin is reached, where spawning takes place and the enervated salmon's lifecycle is ended. The fertilized eggs in the gravel-covered redds remain to perpetuate the cycle. This chapter focuses on the sensory mechanisms that the salmon possess and the environmental cues that they detect to find their way out of the river, around in the sea, and back to the river again with such remarkable accuracy. The chapter reviews and discusses some of the more credible theories that attempt to explain the salmon's return to its home river.