CHONGQING, April 17 (Xinhua) -- The rise and fall of the water level in the Three Gorges reservoir has triggered 166 geological hazards and forced 28,600 people to relocate in Chongqing Municipality since last September, local officials said.

    Since the water levels behind the dam rose from 145 m to 172.3 m on September 28 last year, these geological disasters including landsides and mud-flows have caused economic loss of 539 million yuan (79 million U.S. dollars). No casualties were reported, said Wen Tianping, spokesman of Chongqing government, at a press conference Thursday.

    The people whose houses were liable to suffer damage had moved to safe places where new homes have been built. Some are living with their relatives, he said.

    The 22.5-billion-U.S.-dollar project on the upper and middle reaches of the Yangtze River mainly aims to control floods. The dam usually discharges water before the flooding season so that the reservoir can hold more than 19.3 billion cubic meters of upstream water.

    After the flooding season, the water level is expected to rise to 175 m to generate power and improve navigation upstream.

    The rise and fall of the water level can lead to geological disasters along the Yangtze River. Wen said it needs three or five year or even more for the reservoir bank to stabilize.

    Spokesman of the Three Gorges Project Construction Office of the State Council, which administers the project, did not comment on the statistics from Chongqing.

    "The Ministry of Land and Resources (MLR) has the authority to make conclusions on the geological situation of the Three Gorges reservoir," the spokesman said.

    "According to our observation, the water storage did not cause serious geological disasters. Banks of the reservoir area are stable," Li Lierong, who was in charge of the mitigation of Three Gorges geological disasters, told Xinhua on Friday.

    He led a team to conduct a safety survey along more than 1,000km of embankments during the water storage.

    "But we should continue to treat the unstable sites, as the natural and geological conditions in the reservoir area are complicated," Li said.

    Wen said the Chongqing government, experts and villagers are closely monitoring the geological condition in 2,516 sites where disasters might occur before the flooding season, which comes in June.

    "We have adopted unmanned planes, yachts and off-road vehicles in the monitoring," Wen said. "We have spent eight billion yuan to harness geological hazards. Residents in the reservoir area are safe."