Hydrochemical Processes and Hydrological Separation
in Headwater Basins of the Urumqi River, Tien Shan, China
Fengjing Liu1, Mark Williams2, Junying Sun1, Shousen Zhu1,
Eran Hood2, and Guodong Cheng1
China's cultural practices and heavy reliance on coal burning have resulted in high concentrations of
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tion to high-elevation areas where annual precipitation is dominated by snowfall. In other areas of
the world, significant and severe ecological changes have occurred in terrestrial and aquatic ecosys-
tems where levels of sulfur- and nitrogen-containing compounds are less than those currently exist-
ing in China. As part of ongoing efforts to fully understand the susceptibility of seasonally snow-
covered alpine basins to deposition of atmospheric pollutants, the purpose of this study was to better
understand the processes that control the hydrochemistry of high-elevation headwater basins within
China during snowmelt runoff.
The Urumqi River Basin is located in the Tien Shan mountain range that extends from north-western
China more than 2000 km westward into the republics of Kirgzhia. The research area was the head-
waters of the Urumqi River, with an area of 29 km2 above the Total Control (TC) gauging station.
More intensive studies focused on two headwater basins, each about 2 km2 in area: the glacierized
Glacier No. 1 (G1) and the Dry Cirque (DC), a south-facing and ice-free cirque. Daily samples of
stream water were continuously collected for solute analysis from April 30 to June 8, 1997, at TC,
G1, and DC gauging stations. Snow pits were excavated and core samples were collected on June 8
at G1.
A parametric analysis for mutual regression shows that the solutes of streamflow were inversely
correlated with discharge (e.g., < 0.66 for most solutes at G1) and correlated with Si (e.g., > 0.80 for
most solutes at G1) within a basin, suggesting that the streamflow had strong signatures of soil-
contacted water. Hydrological separations using Si as a tracer demonstrated that the soil-contacted
water represented 40% of discharge at G1, 70% of discharge at DC, and 77% of that at TC. However,
the release of solutes from storage in the seasonal snowpack in the form of an ionic pulse appeared to
be an important process at times. For example, at G1 on May 6, 16, and 24, SO2- concentrations
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were 4.65, 5.97, and 3.91 times the SO2- concentrations at the onset of snowmelt on May 2. Simi-
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larly, NO3 concentrations in streamflow were as high as 3.75, 4.99, and 4.85 times the initial con-
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centrations. Also, the ionic pulse occurred at DC, with significant peaks of Cl, NO3 , and Na+. It is
suggested that both the ionic pulse and contributions of soil-contacted water are important in regulat-
ing the solute contents of the streamflow during the snowmelt season at headwater basins of the
Urumqi River. At present, the resulting streamflow is not sensitive to the acidification.
1The
State Key Laboratory of Frozen Soil Engineering at Lanzhou Institute of Glaciology and Geocryology,
Chinese Academy of Sciences, Lanzhou, Gansu 730000, China
2Department of Geography and Institute of Arctic and Alpine Research, University of Colorado, Boulder,
Colorado 80309, USA
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