Observed changes in streamflow at the headwaters of the Urumqi River, eastern Tianshan, central Asia

The runoff records of streams draining basins with between 0 and approximately 54% glacier cover, located at the headwaters of the Urumqi River in eastern Tianshan, central Asia, have been examined for the purpose of assessing climatic and glacial influences on temporal patterns of streamflow for the period 1959–2006. Runoff in the highest glacierized basin is found to be inversely correlated with the glacier mass-balance data and increased by 165·1 × 104 m3 or 1·5 times on average from 1959 to 2006, whereas flow from a glacier-free basin reflects precipitation changes associated with temperature that may enable either ground ice formation or ice storage release. For the basin with a glacier cover of 18·5%, the runoff increased approximately 355·4 × 104 m3 or 29·6% on average from 1983 to 2006, which underscores expected results based on glacier melt and precipitation increase, especially after 2000. This is due to several possible reasons including enhanced evaporation, groundwater percolation, increased water consumption due to plant colonization and runoff decrease from glacier basins subject to area reduction. From the measurement at Urumqi glacier No. 1 gauging station and a simple water balance model, the glacial runoff during the period 1959–2006 was calculated and found to have increased by 145·5 × 104 m3 a−1 (a factor of 2) over the 48-year span. A significant amount of the increase occurred after 1987, particularly after 1995, and coincides with increases in both temperature and precipitation. Copyright © 2009 John Wiley & Sons, Ltd.