Three Gorges Dam calculated based on the average flow rate at the dam site, assuming the water level is 175 m and the plant gross efficiency is 90.15%. The actual power output in 2008 was obtained based on the monthly electricity sent to the grid. The Three Gorges Dam reached its design-maximum reservoir water level of for the first time on October 26, 2010, in which the intended annual power-generation capacity of 84.7 TWh was realized. In 2012, the dam's 32 generating units generated a record 98.1 TWh of electricity, which accounts for 14% of China's total hydro generation. The State Grid Corporation
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,