| The hydraulic conductivity of riverbed sediment, which directly or indirectly affected the ability of transformation between surface water and groundwater, was the basic parameter with Research on the hydrological processes such as water infiltration and solute transport. In an arid inland river basin, water leakage of runoff was the important source of recharge for the groundwater, which played an irreplaceable role in maintaining the stability of the oasis ecological environment and the sustainable development of agriculture and industry. This paper was to solve the actual problem that the water resources allocation and management lacked of important basis causing by the reason that hydrological process was not clear. Particle sizes of streambed sediment in the upper stream of the Tarim River were analyzed and coupled with data on water temperature and runoff, the spatial and temporal variation of hydraulic conductivity was studied. Then with Darcy's law, the water leakage under different water conditions in each section was clarified. The main results were as follows:(1) Particles of sediment are small and the particle size range is relatively concentrated: particle size of sediment was less than 0.9 mm, the sediment did not contain gravel grains, the content of fine particle group were over 15%, the category was mainly fine grained soil sand and fine grained soils. Along the river, sediment texture gradually became thicker. In the vertical direction of the channel, the content of fine particle group showed a "V" type change obviously in Alar section. Compared with riverbed, Sediment texture of flood plain became thicker, but in Yingbazha section, the change trend of sediment texture is different. The fractal dimension of sediment ranged from 1.92 to 2.41 and the mean was 2.12, which meant the composition of river bed sediments was relatively simple. Fractal dimension can not only reflect the sediment texture but also the comprehensive features of sediment grain size parameters.(2) Sauerbrei's experience values were used to calculate the hydraulic conductivity, within the year the permeability coefficient the change trend of hydraulic conductivity and water temperature were in sync, which all showed a "unimodal" change. The variation of hydraulic conductivity were consistent with and the variation of sand, but contrary to the content of clay and silt. Along the river, the mean of hydraulic conductivity of sampling sites presented the obvious increasing trend from section 1 to section 4, which was 0.053m/d, 0.139 m/d, 0.191 m/d, 0.265 m/d(t=20?), and the discrete degree of hydraulic conductivity between the sampling layers also gradually enhanced. In the vertical direction of the channel, hydraulic conductivity of Alar section is obviously inverted "V" type change, the average of hydraulic conductivity of riverbed and flood plain were 0.531 m/d, 0.439 m/d; by contrast, in Yingbazha section, hydraulic conductivity of flood plain was greater than riverbed's, their means were 0.502 m/d and 0.963 m/d.(3) At the inflow frequency of 12.5%, 50% and 87.5%, the total water leakage in the upper stream of Tarim River were 10.85×108m3?9.94× 108m3?9.13×108m3, and it concentrated in May to October, percent of water leakage among this period were respectively 74.6%, 73.1% and 74.6% of total water leakage at 3 inflow frequency. Under the same inflow frequency, the order of river water leakage is section 1, section 4, section 2, and section 3, and the order of leakage per km is section 1, section 4, section 3, and section 2. Verification results show that calculation error of water seepage is only 2% with the test result. In this paper, the calculation result of hydraulic conductivity and water leakage is reasonable. |
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