Study On The Spatial Variation Of Hydraulic Conductivities Of Yuxi River Streambed Sediments And The Transformation Relationship Between River And Groundwater

In the northwest arid and semi-arid areas in China, there is a close hydraulic contact andfrequent conversion between rivers and groundwater. Among the river water and groundwaterinteractions, the permeability of streambed sediments directly affects the strength of the riverand groundwater hydraulic connection and how much the amount of river water andgroundwater mutual conversion. Therefore, carrying out the river-groundwater transformationrelations and streambed sediment spatial variation of hydraulic conductivity on the researchplay an important role for determining the water exchange between the river and groundwaterand contaminant transport, utilizing river-groundwater resources, maintaining the health ofrivers and groundwater systems ecosystem.This study chooses the Yuxi River in Yulin city as the research object. Combined thein-situ permeameter test and grain analysis to measure and value the hydraulic conductivityof streambed in five reach of Yuxi river. Using SPSS statistical software for a statisticalanalysis on permeability coefficient Kv values, concluded that from upstream to downstream,the average Kvvalue of5reach were respectively14.35m/d,26.34m/d,26.34m/d,26.82m/d and2.86m/d. Testing normal distribution on permeability coefficient Kv value, derivedthat it approximately obey the normal distribution after eliminating outliers. Usingsemi-variance variogram of geostatistics analyzed the spatial variation of streambed sedimenthydraulic conductivity. Obtaining that, in YX-2、YX-3、YX-5reach, spatial correlation ofpermeability coefficient is very strong, and at YX-5reach, spatial correlation of permeabilitycoefficient is medium. Meanwhile, estimated the hydraulic conductivity of streambedsediments from using ordinary kriging interpolation method and concluded the distributiontrends of streambed sediment permeability coefficient Kvvalues in different reach. Throughmeasuring the groundwater temperature in different reach, drew the groundwater temperaturechange curve. Depending on the different characteristics of temperature variation curves,determine the relationship of recharge and drainage between the water and groundwater.When water recharge groundwater, with the increase of the depth of stratum, the groundwatertemperature change slowly, the temperature change curve is relatively flat, groundwaterfinally stable temperature close to the water temperature; When groundwater recharge water, with the increase of the stratum depth, the ground water temperature changes rapidly, thetemperature change curve is relatively steep, groundwater finally stable temperature close tothe groundwater temperature. Obtaining that, in YX-1, YX-2, YX-5reach, water rechargegroundwater, in YX-3, YX-4reach, groundwater recharge water. Meanwhile, according to themeasuring point groundwater temperature variation curve of different time, speculated thatthe intensity of transformation between the river water and groundwater. The study alsofound that in the reach that water recharge groundwater, affected by river effect, the riversediment was pressed, the permeability coefficient is relatively small, in the reach thatgroundwater recharge water, affected by river effect, the river sediment was loosed, thepermeability coefficient is relatively big.Finally, through the above work, comprehensively analyzed the relationship between theYuxi river and groundwater and laid a good foundation for further research in the futurework.