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In the past 40 years, stream water qualities in the south part of Tianshan Mountain have changed greatly because of human activities. Many canals have been built to transfer stream waters for irrigation and farmland desalination. For example, the irrigated area has increased more than 4.0 x 10(5) ha upstream of the Tarim River, and now takes almost 40% of the stream water for agriculture. Flow statistics of the lower Tarim River from the last forty years, show stream discharge in middle stream and downstream has decreased about 50% and 85%, respectively. As a result, in the lower Tarim Basin, many lakes have disappeared from the desert, and near half of the farmlands have been lost.

Analyses from 52 sampling points on streams draining the south part of Tianshan Mountain show that about 37% of streamwaters were Ca2+-HCO3- type and more than 40% either Na+-Cl- type or Na+-SO42+ type. The former type prevailed in natural hydrology conditions. The water in latter type was found streams in affected by agricultural activities. Desertification and salinization are twin problems that must be dealt with at the same time and linked by careful water balance management.