The plateau or highland region which forms the waterparting between the Tarim basin on the east and the Syr-darya catchment area on the west.
It used to be supposed that the Tian-shan confronted the basin of the Tarim with a steep, wall-like versant.
And Otun-koza at 2390 ft., facilitate communication between the basins of the Tarim and the Ili (Dzungaria).
The principal stream is, of course, the Tarim, about 1000 m.
The basin of the Tarim contains, indeed, numerous other streams, most of them summer torrents seaming the flanks of the encircling mountains, but once no doubt affluents of the Tarim, though now all swallowed up in the desert soon after quitting the shelter of the mountains.