According to the results revealed by the Ministry of Environment on the "water quality assessment for the 1st quarter of 2003", the water quality of the Korea's four major rivers showed an overall improvement compared to the same period last year.

The quality of water in the Han River Watershed has continuously maintained the Water Grade I, with BOD level of less than 1.0 mg/L. Notably, the quality of water in Paldang Lake has improved from 1.3 mg/L in the fourth quarter last year to 1.0 mg/L this year. However the downstream regions, which maintained the Water Grade III for the last three months, became worse, with BOD level of 5.1 mg/L in Noryangjin and Gayang.

Water quality in main areas of Nakdong River Watershed (Andong, Goryeong, Namji, Mulgeum and Gupo) has continuously maintained the Water Grade I~II ever since last year. Especially Mulgeum area showed significant improvement from BOD level of 3.9 mg/L last year to 2.7 mg/L this year, due to the doubled amount of dam water discharge.

Although the water quality in upper stream regions of the Geum River Watershed showed improvement, due to about 4.7 times increase in dam water discharge compared to last year, the quality of water in downstream regions became little worse, with increase in the BOD level by 0.1~0.2 mg/L.

In Yeongsan River watershed, the water quality of Gwangju area also improved, with decrease in BOD of 0.9 mg/L, but downstream areas (Naju, Muan) became worse, with increase in BOD level by 0.3~0.4 mg/L.

Juam Lake in Seomjin river maintained a fairly good water quality with BOD level of 0.6 mg/L, a significant decrease in the pollution level from 1.3 mg/L last year.