China has said it will spend more than $1.2bn cleaning up the Songhua River along the Russian border after it was polluted by toxic chemicals last year.
Mains water supplies were cut off in Harbin for several days
Water supplies were cut off to millions of people following the benzene leak.
The clean-up plan will fund more than 200 projects designed to reduce industrial pollution and improve sewage treatment and water quality.
November's spill strained relations with Russia and focused attention on pollution problems in China's rivers.
About 3.8m people in the northern Chinese city of Harbin lost their water supplies for up to five days after 100 tonnes of benzene and nitrobenzene leaked into the Songhua.
The spillage was caused by an explosion upstream at a PetroChina chemical factory in the north-eastern province of Jilin.
Announcing the 10 billion yuan Songhua clean-up plan, the State Bureau of Environmental Protection promised tougher punishment for officials responsible for incidents of pollution and stricter monitoring.
Chinese and Russian officials recently allayed fears that the melting of river ice would release further pollution into the river.
The Songhua feeds into the Amur river on the Russian border, affecting water supplies for more than 500,000 people in the Russian city of Khabarovsk.
Meanwhile, officials in China's south-western municipality of Chongqing announced that safety concerns had forced workers to abandon an attempt to plug a leaking gas well.
Some 15,000 residents have been evacuated from their homes, state news agency Xinhua reports. Local officials have warned they are in urgent need of supplies.
People have also been warned against drinking from a nearby river after gas field workers noticed gas bubbling into the water on Saturday.
In the four months since the Songhua incident, China has suffered a further 73 major spills, Xinhua says.
The Ministry of Water Resources estimates that 40% of water in China's 1,300 major waterways is fit only for industrial or agricultural use.
The north-eastern province of Gansu, on the Yellow River, is to spend nearly five billion yuan ($623m) on improving water quality by 2010, Xinhua reports.
Neighbouring Shaanxi has allocated 4.5 billion yuan ($561m) to clean up the Weihe River.