Xiaonanhai Dam total of 338 freshwater fish species have been identified on the Yangtze. 189 live in the area — currently a preservation — and many of those are found in no other river basin in China. An official study by the Yangtze River Commission in 2003 concluded that the Xiaonanhai dam could not be recommended due to its "unremarkable economic returns". According to "Chongqing Daily", project cost per-kilowatt is triple that compared with other projects along the Yangtze: with total investment estimated at ¥32 billion, the project will cost ¥16,000 per-kilowatt of capacity, whereas the Three Gorges dam, Xiluodu Dam and
Three Gorges the river along vertical fractures, forming precipitous cliffs. When the river flows through areas of softer sandstone and shale, which have less resistance to erosion, the erosive effect is increased, carving wide valleys. There are different theories on how the Three Gorges were formed, but geographers and geologists have generally reached a consensus, believing mountain folding in the east of Sichuan Province and the west of Hubei Province, including the Wu Mountains (), were the outcome of the Yanshanian movement () around 70 million years ago. The gorges run from southwest to northeast, then turn, and from west to east,