The water level in the Three Gorges reservoir rose to its maximum level of 175 metres on 26 October, raising electricity output to capacity at the world’s largest hydropower plant for the first time, said Cao Guangjing, chairman of the China Three Gorges Corporation.

Mr Cao said raising the water level to capacity was a milestone in the construction of the reservoir, and that the achievement answered some of the concerns raised at the beginning of the project over issues such as the functioning of key equipment, water quality and sediment control.

This was the third attempt to raise the water level to capacity since 2008. Previously, drought conditions and geological concerns prevented the target from being achieved. Last year, Caijing magazine revealed a government report warning that rising water levels were increasing landslide risks as the soil around the dam became more saturated and unsettled. The article cited an inspection report by local officials that identified nearly 700 areas vulnerable to geological damage, 587 of them possible landslide spots.

The water level will be maintained at 175 metres for about two months for surveillance purposes before being allowed to fall to between 145 metres and 175 metres, depending on flood control needs.

Water quality in the Three Gorges reservoir area in Chongqing municipality has remained stable since the latest trial to raise the water storage level to 175 metres started earlier this year, according to the municipal government. Chongqing has built 94 domestic sewage disposal plants and 48 rubbish disposal plants to protect the local water environment.