Hangang is a river that flows horizontally across the midsection of the Korean Peninsula. It is 494.4 km long and has a drainage area of 25,953 km2, or 35,770 km2 including the section in North Korea. Lying mainly in Gangwon-do and Gyeonggi-do, the Hangang watershed ex- tends into Seoul, Incheon, Chungcheongnam-do, and Chungcheongbuk-do. Hangang is largely divided into Bukhangang (North Hangang) and Namhangang (South Hangang). The two rivers join at Yangsu-ri, Yangseo-myeon, Yangpyeo- ng-gun, Gyeonggi-do, flow through Seoul, and finally drain into the Yellow Sea at Bogugot-ri, Wolgot-myoen, Gimpo-si. Namhangang, the main stream of Hangang, originates in Geomryongso of Geumdaebong (1,418 m) in Changjuk-dong, Taebaek-si, Gangwon-do. Dalcheon, Sumgang, Cheongmicheon, and Bokhacheon are some of the streams that ow into Namhangang. Bukhangang,
which is the largest branch of Hangang, origi- nates in Danbalryeong (1,241 m), Geumgang-gun, Gangwon-do and is joined by Yangguseocheon and Soyangang.
Nakdonggang, which flows south through the southeastern part of the Korean Peninsula, is 510.3 km long and has a drainage area of 23,384 km2. The Nakdonggang watershed is located across Busan, Daegu, Gangwon-do, Gyeongsangnam-do, and Gyeongsangbuk-do, and also lies along the bound- aries of Jeollanam-do, Jeollabuk-do, and Chungc- heongbuk-do. Nakdonggang stems from Hwangji Pond on the eastern side of Hambaeksan in Tae- baek-si, Gangwon-do and discharges into the South Sea through an estuary dike and delta in Busan. Seonakdonggang branches off at the delta located at the river mouth of Nakdonggang.
Geumgang starts in the center of the Korean Peninsula and ows northwest and southwest. It is
397.8 km long with a drainage area of 9,912 km2, and its watershed lies mainly in Sejong-si, Dae- jeon, Chungcheongnam-do, Chungcheongbuk-do, and Jeollabuk-do. Originating in Tteunbongsaem Spring of Sinmusan (896.8 m), Subun-ri, Jang- su-eup, Jangsu-gun in Jeollabuk-do, Geumgang flows northwest through Daejeon, Daecheong reservoir, and Sejong, and then flows southwest through Gongju and Buyeo before finally dis- charging into the Yellow Sea. Until the comple- tion of the Geumgang Estuary Dike in 1990, high tide seawater would ow upstream as far as Gang- gyeong-eup, Nonsan-si, Chungcheongnam-do.
Seomjingang, owing south in the southern part of the Korean Peninsula, is 223.9 km2 long with a drainage area of 4,911 km2. It has a watershed that is located across Jeollanam-do, Jeollabuk-do, and Gyeongsangnam-do. Starting at Demisaem Spring on Palgongsan (located at the boundary of
Jinan-gun and Jangsu-gun, Jeollabuk-do), Seom- jingang ows through Jeollanam-do and Gyeong- sangnam-do, and discharges into the Gwangyang Bay in the South Sea.
Yeongsangang is located in the southwestern region of the Korean Peninsula. It is 129.5 km long with a drainage area of 3,467 km2, and has a watershed that lies mainly in Jeollannam-do, Jeollabuk-do, and Gwangju. It originates in Yong- so of Gamagol in Yongyeon-ri, Yong-myeon, Damyang-gun, Jeollanam-do, runs through the Naju Plains, and finally reaches the Yellow Sea at an estuary dike. The dike was constructed in 1981 to prevent seawater from owing upstream at high tide. Hwangryonggang, Jiseokcheon, Go- makwoncheon, and Hampyeongcheon are some of the streams that ow into Yeongsangang.