[VIEWPOINT]The dammed North is a problem

The Bukhan River dwindled into a small stream after North Korea finished construction of its Mount Geumgang Dam and filled the reservoir behind it.

The dam, also known as the Imnam Dam, is one of several built by Pyeongyang recently to increase its hydroelectric resources. The North reportedly diverted the water course of the upper reaches of the Bukhan River. The diverted flow passes through a 45- kilometer-long tunnel built by the North in the Taebaek Mountains, which resulted in the depletion of water in the lower reaches of the Bukhan River.

Our own hydroelectric generators at Hwacheon, Uiam and Chuncheon suspended operations several months ago and power generators at Cheongpyeong and Paldang are also seriously affected by the North Korean dams.

The government has observed that the water inflow at Hwacheon Dam dropped from 2.93 billion metric tons last year to 2.58 billion metric tons this year, a 12 percent decrease compared to an average year's flow. The government said this is not a serious problem, because the change resulted in only a 2 percent decrease in the water flow of the entire Han River system.

But the government's optimism is based on outdated statistics, compiled before the Bukhan River was dammed by North Korea. The inflow at Hwacheon Dam in April 2001 dropped by 80 percent compared with an average April. In May, the inflow fell 93.5 percent, making it impossible to operate the hydroelectric generators. Water flow at Hwacheon Dam in 2001 decreased by 1.77 billion metric tons, not 350 million metric tons as the government claimed. The figure almost coincides with the 1.8 billion metric tons of precipitation in 2001 in the Imnam Dam drainage area on the upper reaches of the Bukhan River. Hwacheon Dam reportedly saw a drop of 60 percent of its normal annual water inflow.

The water level of the Han River at Seoul last year dropped one or two meters compared with the previous year's level. This may be good news during the rainy seasons, when the Han River overflows, but the builders of the Gyeongin Waterway will have to dredge several meters deeper, and ship navigation will be more difficult because of shallow water in several areas of the river.

In the upper reaches of the Bukhan River north of Hwacheon Dam, there are tumbled rocks and other signs that the water flow was heavy in the past. Boats used to ply the river. But now the water is shallow enough for people to cross it unaided. People could cross the river even during the peak of the rainy season last year. Normally, the river is 30 meters deep.

The diversions could also lead to a weakening of the river's ability to purify itself, raising concerns about the water quality at the Paldang dam. The destruction of the ecosystem could accelerate.

Why does the Korean government not protest to the North about this issue? Last winter, South Korea was even flooded with 350 million tons of muddy water when a dam in North Korea collapsed.

North Korean officials told me there were no plans to build a dam at Imnam when I raised questions in 1996 about its plans to block the Bukhan River three or four years in the future. But the North not only built the dam; it is now working to increase its capacity. It has become clear that South Korea's plan to counter any water shortage by building Donggang Dam and Bamseonggol Dam is useless.

The government raised no protest with the North about its initial construction work on the Imnam Dam in 1999 despite an earlier pledge that it would deal strongly with the North if it showed any signs of launching the project. Nor did the government take any measures in 2000, amid the festive mood of the North-South summit.

The problems of flooding in the southern reaches of the Imjin River can be solved. Since the North is building several dams along the river, the matter will be dealt with sooner or later. But there is no way to compensate for the 1.8 billion metric tons of water in the Bukhan River taken by the North. If the government chooses to remain silent over the blockage of the Bukhan River, it is giving tacit consent to the North's unjustified conduct.

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The writer is a professor of international law at Seoul National University.

by Rhee Sang-myon