The evidence shows “按遼薊三千餘里，冠蓋所往來，舟車所要衝。統浿～四十二州，川蜀之殷富，蘇杭之佳麗。” 遼薊 means 遼地 (current 辽宁) and 薊地 (current 河北, 北京, 天津), 川蜀 means current 四川 and 重庆, 蘇杭 means 蘇州 (苏州) and 杭州, so 浿～ must be one or two places. 《舊唐書·卷三十九·志第十九》 shows “高麗本五部，一百七十六城，户六十九萬七千。其年十二月，分高麗地為九都督府，四十二州，一百縣，置安東都護府於平壤城以統之。” The year (其年) means 總章元年 (aka 668 A.D.), so that 四十二州 means Koryo (高麗/고려). 浿水 means current Taedong River in current Phyeongyang and other cities and provinces of DPRK/North Korea, so ～ may be the other river in Koryo, but I can’t find which one is.

It looks a very important geographical term in Korean. We should take it more carefully.

Thanks for Huang Junliang’s help, the river should be 薩水 in the Chinese ancient books, which is current Ch'ongch'on River (淸川江/청천강) in DPRK/North Korea. 《北史·列傳·卷七十九》 shows “東濟薩水，去平壤城三十里”. 《朝鮮王朝實錄》 shows “平安道有急, 則將長山串以西兵船, 載於阿郞浦, 則平壤 浿江、安州 薩水漕可通也。” 安州 is under Phyeongannamto (平安南道/평안남도) now.

See #6054