Worries over Three-gorge dam

i'm shocked to learn that dams cause so many troubles to local environment. The three-gorge dam in China has 5 major problems
(1) because of the imbalanced distribution of water resources, the chinese government mandates that water should be redistributed from south to north to enhance the development of north. But the problem of shortage of north china is largely due to man-made destroy of forests and wetland. Let alone the problem of fairness, government somewhat misses the real problem and causes some real trouble. For example, the dam damages the equilibrium of water supply and in 2006, sea water poured into Huangpu River in Shanghai 3 times because of the man-made change of river flow direction.
(2) the reservoir to some extent becomes a man-made big water pool and inevitably it changes the local weather. IN 2006, Chongqing suffered from unusual scorching weather. The ground temperature even approached 77 degree centigrade.
(3) the existence of dam break down the water path so that some kinds of fishes cannot swim back to upper reaches of Changjiang River to reproduce. The biodiversity is damaged.
(4) Changjiang River brings down to lower reaches delta large amount of silt. Silt stacks and forms the basis of Shanghai. The existence of the dam obstructs Changjiang river (reduce the risk of floods) but at the same time stops the silt. Without the continuous protect of silt, sea water "erodes" Shanghai.
(5) The construction of the dam stops the normal flow of the river, some chemical materials gather and eutrophication of water occurs.