中更新世晚期以来黑河流量逐渐减少,由外流河变为内流河,由统一水系变为各自的独立水系,中、下游由地面水和地下水相互转化,不少河道随流量变化及新构造运动影响而改道,从而沿岸新老绿洲互不相连。

The Hexi desert and oases region of Gansu Province belong to internal drainage area where all rivers originate from Qilian Mountains. From east to west, the rivers can be divided into four drainage systems; Shiyang river system, Hei river system, Shule river system and Harteng river system. Har-teng river flows into Suganhu Basin which lies in the northern margin of Caidamu Basin, while all theot her three drainage systems flow into Hexi Corridor, Hei river is the greatest and longest of all these rivers, stretching north to Alashan Plateau. This paper mainly discusses the distribution and change features of Hei river system based on the ancient and modern maps and salt content in ancient rivers and lakes and deduces how it has changed from exterior river to interior river, from integrate drainage system to many seperate drainage systems, from a river with its middle and lower reaches in the same course to a special river which changes alternately between surface water and undergronud water in the middle and lower reaches, and forming many oases of varying sizes along the bank of the river in certain regions.