Dams and Impounded Rivers - River Dynamics and Integrated River Management - page 439

The lower stream stage is 62-78 m and the maximum flow discharge for navigation is 56,700 m 3 /s. The
bottom level and the highest water level of the five step locks are 130-179 m, l19.25-161 m, 98.5-140.25 m,
77.75-l19.50 m, 57-98.75 m, respectively.
Fig. 7.35 Profile of a turbo-generator
The shiplift and the temporary ship lock use one approach channel, which connects to the lower approach
channel of the permanent ship locks. The upstream approach channel of the ship locks is 2,113-m long
and 180-m wide and the downstream channel is 2,722-m long and 180-m wide. One line of the ship locks
is for navigation upstream and one line for downstream. For each step of the ship lock, only 12 minutes
are needed to fill or empty water. The annual water consumption of the ship locks is 3.4 billion m 3 . The
ship lift was used during the construction period and will be used as a fast channel to go through the dam
after impoundment of the reservoir. The size of the lift cabinet will be is 120 × 18 × 3.5 m and may carry
a 820 seat passenger ship and a 1,500 t freight ship. The bearing capacity is 11,800 t including the ship,
9000 t water and 2,800 t of its own weight. It takes 42 min for a ship to pass the dam through the ship lift.
The ship lift can transport 5 million people and 6.26 million t of goods every year.
The temporary ship lock was used during the second phase of construction. As the flow discharge was
less than 20,000 m 3 /s, ships navigated through the temporary open channel. Only a few kinds of ships with
low navigation capability had to go through the temporary ship lock. If the flow discharge was higher
than 20,000 m 3 /s, however, no ship could navigate through the open channel and all would have to use
the temporary ship lock. The ship lock is 240-m long, and 24-m wide with water depth 4 m. Its working
upstream water level is 65.7-75.5 m and the lower water level is 65.6-75.8 m. The maximum stage
difference is 3.7 m. The annual transportation capacity is 9-11 million tons.
The temporary open channel on the right side was mainly for conveying flood flows and ship navigation
during the second phase of construction phase. The open channel is able to discharge a 50-year flood flow,
or a discharge of 79,000 m 3 /s. The open channel was 3,410-m long with minimum bottom width of 350 m.
7.4.1.3 Construction of the Three Gorges Project
Phase I (1994-1997) —The TGP is being constructed in three phases, as shown in Fig. 7.36. Preparations
for construction of the dam were done in 1993 and 1994. Formal commencement was declared on Dec.
14, 1994. There was a small island, Zhongbao Island, at the dam axis, which divided the river into two
branches. The right branch, Haohe branch, was dry in the low-flow season and floods flowed through it
before the project. In the first phase, an earth coffer dam was built to enclose the right branch channel.