"We have not decided to open all the 16 dammed pools immediately and completely. That's because five years have passed since the pools were established and there have been some changes in the environments there," the statement said.

As the government is trying to restore the environments in the rivers through a comprehensive and considerate analysis, it has decided to initially open the six dammed pools, it said.

"For the next month, the government will closely monitor any developments and emergencies that may arise and compare the environments before and after the opening," a ministry official said.

As for the remaining 10 dams, the government plans to gradually open them after checking for their possible environmental impact and effects on farming in nearby areas, he said.

The 16 dammed reservoirs are on the country's Han, Nakdong, Geum and Yeongsan rivers, which underwent a mega-scale restoration project to prevent water shortages, improve water quality and create riverside tourism spots under the Lee Myung-bak administration whose five-year term ended in February 2013.

As some of the dammed pools turned completely green with algae after the massive development project, environmentalists have called it a failure and claimed they have caused serious damage to the environment.

On May 22, the presidential office Cheong Wa Dae ordered an inspection of the four rivers development project. It will be the fourth round of inspections carried on on policies implemented by previous governments. There are two probes underway for policies made under the Lee government and one carried out while impeached President Park Geun-hye was in power.

Under the 22 trillion won ($20 billion) project, the Lee government spent 11.9 trillion won, about half of the budget, on works on the Nakdong River, the longest river in Asia's fourth-largest economy. About 3.7 trillion won was spent on the Han River, with 3.4 trillion won spent on the Geum River and 3.4 trillion won on the Yeongsan River.

Eighty-seven old dams were rebuilt, 16 new dams were constructed and some 300 kilometers of riverbank was reinforced on the four main rivers. (Yonhap)