China launched nearly 8,000 water clean-up projects in the first half of 2017 with projected total investment of 667.4 billion yuan ($100 billion), the environment ministry said on Thursday.

The projects were devised as part of a 2015 action plan to treat and prevent water pollution, and cover 325 contaminated surface water sites across the country, the Ministry of Environmental Protection (MEP) said in a notice.

A total of 343 contaminated sites had been identified, meaning that 95 percent had drawn up plans to bring water quality up to required standards, it said.

However, it noted that some regions were still behind schedule when it came to meeting their 2017 water pollution goals.

Across the country, 1,762 companies have taken clean production methods to prevent water pollution, accounting for 84.6 percent of companies needing to make the transformation.

China has also changed 75,000 underground oil tanks to two-layer tanks or added seepage prevention measures.

With China desperate to increase supplies to guarantee future food and energy security, it promised in 2015 to make significant improvements in its major waterways and curb untreated wastewater from highly polluting sectors like mining, steelmaking, textiles, printing and oil refining.

The MEP said this month that overall water quality had improved in the first half of 2017, although some regions registered an increase in substandard samples over the period.

China grades its water in six bands, with the lowest "below grade 5" considered unusable even for industrial or irrigation purposes and described as "black and stinky" water.

Of 2,100 "black and stinky" sites identified, 44.1 percent had completed treatment projects in the first half of the year, the ministry said, noting that the provinces of Hebei, Shanxi, Liaoning and Anhui had fallen behind.

In a bid to protect rural water supplies, China also identified 636,000 square kilometers of land that would be made off limits to animal husbandry, and it shut 213,000 livestock and poultry farms in the first six months.

The ministry also said 809 new household sewage treatment facilities were built in the first half, but the regions of Tianjin, Jiangxi, Inner Mongolia, Guangxi, Xinjiang, Hubei and Guangdong were behind schedule, it said.

China said on Wednesday that it has already appointed 200,000 "river chiefs" throughout the country as part of a new system aimed at making local officials more accountable when it comes to improving water quality and curbing pollution.