Preparations for storing water in the Three Gorges reservoir have entered the final stage.

The reservoir's water level is set to rise from 80 metres to 98 metres by June 1.

The water level will then reach 135 metres by June 15.

Cao Guangjing, deputy general manager of the China Three Gorges Project Development Corp, said the first main water-storage phase is proceeding on schedule.

Under the next two phases, the water level is due to rise to 156 metres by 2006 and then to 175 metres by 2009.

The massive project is expected to cost 180 billion yuan (US$21.68 billion). Work on the world's biggest hydropower project started in 1992 and is expected to finish in 2009.

"This year is a milestone time for the project,'' said Cao.

In addition to water storage, trials lasting an unspecified time period will begin on June 16 on a 6.4-kilometre-long ship lock, the longest in the world.

Two power-generating units, each with a capacity of 700,000 kilowatts, will be put into operation in August and another two will go into use in October.

Another official with Cao's corporation said precautions had been taken to guarantee the safety of the water storage and other work.

The official, surnamed Zhang, said a safety monitoring system has been set up in the dam next to the reservoir in preparation for storing water and navigation.

The dam built by Zhang's corporation is 2,309 metres long and 185 metres high. Zhang said the corporation has adopted the world's most advanced safety monitoring methods.

To date, more than 5,100 monitoring instruments have been installed on the dam and 8 million items of data have been input into the monitoring system.

Zhang said that the monitoring system is able to monitor possible deformations of the dam, crevices, hydraulic problems, ageing of materials and leaks.

All of the monitoring equipment is currently operational.

To facilitate navigation between the dams of the Three Gorges project and Gezhouba project, a unified management system will take control on June 1 of the electricity generated by China's two largest water-control projects on the Yangtze River.

The Three Gorges Project Development Corp will take over management of flood discharging, water storage, power generation and shipping for both projects.

Most of the preparations for the unified management are ready and the automatic reservoir-control system is already operational.

The Gezhouba project was completed in 1989 and is located in Yichang in Central China's Hubei Province, about 40 kilometres downstream from the Three Gorges project. The Gezhouba project boasts a generating capacity of 2.71 million kilowatts, along with a ship lock and flood-discharge facilities.

The Gezhouba project will be required to maintain its discharge volume at a minimum of 3,410 cubic metres per second to ensure the passage of shipping downstream.