| Yili River Valley is located in northwest China's arid oasis,Eurasia hinterland,mild and humid climate,also has abundant water and land resources.However,with the developing of local socio-economic,the demand of water resources is increasing,and the environmental problems caused by unreasonable development and utilization of water resources are gradually emerging.The river water of Yili River is the main recharge and excretion items of groundwater,river water and groundwater are closely related and frequent conversion.The hydraulic conductivity of river sediments in different regions also determines the strength and the intensity of transformation of river water and groundwater.Therefore,it has significant theoretical and practical to find out the spatial variability of hydraulic conductivity for riverbed sediments and the relationship between river water and groundwater conversion.The Yili-Kunes River in Xinjiang was selected as the research object in this paper,and the hydrogeological conditions were investigated and analyzed.The vertical hydraulic conductivity(Kv)for riverbed sediments was measured by four methods: falling head method,porous media vertical osmometer method,particle analysis method and double-rings method.The spatial variability of Kv was researched by comparative analysis and statistical method.The groundwater temperature change with time and depth is analyzed,and the relationship between river water and groundwater transformation was studied by temperature tracer method.The results of research show that:(1)The results of hydraulic conductivity tested by four different methods have little difference,basically less than 5 m/d,which is in accordance with the actual results,and according to the result of the tested Kv from big to small,the test method is sorted as follow: double-rings method,porous media vertical osmometer method,falling head method,the largest error of the test is measured by particle analysis method.(2)In the Yili River Valley,whether the north and south sides of the perpendicular river,or along the river direction from upstream to downstream,the hydraulic conductivity all obey normal distribution.And the normal test results of the vertical hydraulic conductivity measured by falling head method along the river course are more consistent with the normal distribution than the Kv in the vertical river direction.(3)The spatial variability of the hydraulic conductivity for the sediments in the Yili-Kunes River Valley is analyzed by traditional statistical method.It has been found that in the regional distribution of the study area,whether the north and south sides of the perpendicular river,or along the river direction from upstream to downstream,the spatial variability of all the hydraulic conductivity is moderate-strong.The spatial variability of the hydraulic conductivity along the river direction is stronger than the vertical river gully,and the spatial variability of hydraulic conductivity in the upstream sediment is stronger than in the downstream.(4)The changing curve of the temperature of the shallow groundwater with time and depth measured by the temperature tracer test can be found that the shallow groundwater temperature is affected by the heat exchange and the fluctuation is more obvious when the river water is supplied by groundwater.The fluctuations of shallow groundwater temperature are gentle because of the buffer action of groundwater temperature when the groundwater is supplied by river water.(5)By comparing the results of the temperature tracing method and the hydrodynamic method to the vertical seepage velocity between the river and the groundwater,it can be found that the results of the two methods match well,which is between 0-8 cm/d.As a new method of hydrogeology research,temperature tracer method has high accuracy in relation analysis of surface water and groundwater transformation and calculation of hydrodynamic exchange capacity in streambed saturated zone. |
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