President Moon Jae-in’s move to reverse the effects of a controversial damming and dredging project has run into an unexpected snag: South Korea may be entering one of the most severe droughts in decades.

From Thursday, the government will release water from six of the 16 dammed pools on four major rivers, the first step after Moon’s order earlier this month to review from scratch the previous Lee Myung-bak administration’s 22 trillion won ($19.5 billion) project.

The water levels of the dammed pools will gradually drop by 2-3 centimeters per hour from 2 p.m. on Thursday, officials from the environment and land ministries said in a joint press briefing Monday. The discharge is expected to lower water levels by between 1.25 meters and 2 meters in total in six weir dams built on three of the four rivers -- Nakdong, Geum and Yeongsan.

“We have not decided to open all of the 16 dammed pools immediately and completely, because five years have passed since the dams were established and the ecosystem has adjusted to the change already,” the ministries said.

They emphasized that discharging that amount of water will not affect irrigation for nearby farmers, noting that rice planting season has just begun.

Some experts and farmers expressed concerns that the timing could not be more wrong.

“Based on calculations, South Korea is now facing the worst drought amid serious climate change, which experts forecast will cause the driest season in 2025,” warned professor Byun Hee-ryong of Pukyung National University.

As of the end of May, the country saw an accumulated precipitation of 161.1 millimeters, only half the usual level of 292.7 mm.

Low precipitation has led to low water levels in reservoirs. Boryung Dam, a source of water for eight cities and counties in South Chungcheong Province, currently has an “alert” placed on it because it has insufficient water for agricultural use.

Environmental activists said the government’s decision was neither drought-busting nor capable of cleaning waterways.

“The release of water from only six dammed pools and lowering the water level by up to 1.25 meters will do very little to improve the water quality or remove algae,” the Korea Federation for Environmental Movements said in a statement.

“Discharging such a small amount water, which is less than 10 percent of at least 1 billion tons of water stored there, will not fundamentally solve the algae problem,” said civic activist Lim Hee-ja.

Along with the immediate release of water from the dammed pools, Moon ordered the execution of a drought countermeasure plan in advance.

“Drought countermeasures must not be a temporary plan, but should fundamentally tackle the serious drought problem here,” Moon was quoted as saying.

When rice planting season ends, the government will further lower the water level by 50-100 centimeters in October and open all dammed pools to the lowest limit by the end of 2018, Cheong Wa Dae said.

“In an effort to restore the environment in the rivers through a comprehensive and considerate analysis, the opening of another 10 pools will be decided depending on the outcome of future studies on their impact on the ecosystem,” said Cheong Wa Dae spokesperson Park Soo-hyun.

Cheong Wa Dae said ministries and a related task force will monitor water levels to effectively deal with problems following the opening of dams.

By Kim Da-sol (ddd@heraldcorp.com)