Kwangpho is the third largest natural lake of Korea. It is in the coastal flat area of South Hamgyong Province.
Kwangpho was a bay of the sea and turned into a lagoon by the seaside upheaval and sedimentation.
The lake covers an area of 9.02 square kilometres and its circumference is 31 kilometres. It is 0.6 metres deep on an average and 1.1 metres at the deepest.
The water had much salinity under the influence of the sea, which decreased as the lake was fed by more than 60 small streams.
The lake is gradually becoming shallower because of the sedimentation of the streams. A delta has been formed at the mouth of a stream, dividing the lake into upper and lower parts.
The lake bed consists of mud and sandy soil. The upper part is covered with mud and the lower part with soil mixed with 80 percent of sand.
The main water source is atmospheric precipitation which flows into the lake in the form of stream and underground water. The total volume of water is more than 308,660,000 cubic metres a year.
For its rich water source, the lake is used as a large-scale duck farm, freshwater fish farm and oyster bed and for irrigation.
Kwangpho has been registered as a natural monument of the country as it is of important scientific value in studying the rhythmic movement, denudation and sedimentation of the crust and the change in distribution of the sea and rivers.