Sitting on a tributary of China's Yangtze River, Gangkouwan hydropower station does more than generate electricity.

The facility's reservoir protects 36,600 hectares of farmland, towns, villages and roads from major floods.

Water flow is managed to ensure crops are irrigated and in line with the reproduction cycle of fish downstream.

The power station blends in well with lush plantations nearby, clean running water underneath and the picturesque mountain ridges on both sides.

Hydropower generating facilities along the Yangtze River are undergoing majors overhauls to make them as eco-friendly as Gangkouwan. If they cannot reduce their ecological impact, they will be shut down.

Their fate was made clear in a document on development along the Yangtze River, approved earlier this week by China's top leadership. In the document, environmental protection trumps economic development. Binding environment constraints, legislation on river protection and incentives for local governments are among measures to support greener development.

The Yangtze winds its way across China from west to east for over 6,000 km. Its 990 billion cubic meters of water has the potential to generate 1 trillion kilowatt hours of power, around half of the power China generates each year.

Gangkouwan hydropower station, in Xuancheng City in east China's Anhui Province, generates 100 million kilowatt hours per year. The same amount of power would require 30,000 tonnes coal to be burned, which would generate 60,000 tonnes of carbon dioxide.

"The hydropower station should not only contribute to the local economy, it should be something for the environment, too," said Xiao Yonghui, the power station's general manager.

It's a cleaner source of energy compared with fossil fuel as it helps mitigate green house effects and acid rain. But environmentalists have voiced concern over the ecological impact hydropower stations have on their locality. Large hydropower projects in the upper stream of the Yangtze River have been blamed for causing droughts as they disrupt water flow.

But such alternative energy will be an inevitable choice for a country facing mounting challenges to stop air pollution turning from bad to worse after decades of over-reliance on fossil fuel.

In addition to helping the country wean itself off fossil fuels, these power generation facilities are also being approved and constructed amid an ongoing infrastructure boom used by the government as a backstop for slowing economic growth.

Officials are well aware of the problems with hydropower development in the past. Some facilities have sucked downstream rivers dry and displaced residents.

The State Council, China's cabinet, said during a meeting late last year that hydropower projects should be designed, constructed and operated with the local environment and communities in mind.

"We have dismantled over 100 small hydropower station over the past two years and these sites are now farmland," said Yang Youzhi, a local official responsible for managing hydropower works in Anhui. "The reason they are gone is that they over-dam rivers and were almost worn-out."

Remaining facilities will get a boost in power generation capacity to make up for capacity lost due to the dismantling of old stations. They also need to adjust water flow in consideration with the natural environment, industrial and residential water usage needs and other water-related emergencies.

The provincial government also requires relevant authorities to take concrete actions to resume water flow disrupted by hydropower stations. Ecological protection is also featured heavily in the authorities' review of plans to construct new facilities.

In Zhejiang Province, next to Anhui and further down the lower reaches of the Yangtze, an ecological restoration program is underway around the province's hundreds of hydropower stations.

The program aims to restore the ecosystem around 300 facilities, while another 150 facilities will be phased out in the next five years.

What decides the fate of existing hydropower stations, Yang said, is their ability to deliver ecological benefits. If they cannot, "they don't have a reason to be there any longer."