Spatial Variability Of Streambed Hydraulic Conductivity In Golmud River

The hydraulic conductivity K of streambed sediment is one of the most importanthydrogeological parameter, which influencing the conversion relationship between riverand groundwater, the amount of infiltration from river, excretion from aquifer to riverand the mining capacity of riverside wells. Permeability coefficient represents the ability to transfer water in porous media, accurate estimate riverbed permeability is very important for the analysis of river ecosystems and their relationship in a groundwater basin,while helping to understand the exchange of water and the extent of Water migration betweenn river and groundwater, it also may solve a series of problems related tothe hydrogeological. In this paper, In-situ Permeameter Test was used to determine thehydraulic conductivity of riverbed sediments in Golmud River.Using traditional statistical methods and geostatistical methods to do a thorough analysis of normality distribution and variability of measured data.Research findings obtained following aspects:Ⅰ: Spatial variability of streambed hydraulic conductivity with depthStreambed hydraulic conductivity K decrease with depth, sediments K reaches themaximum of52.25m/d at0~20cm and reaches a minimum of0.69m/d at30cm, then reaches a stable value in40~50cm. River bed sediments of permeability coefficientK value decreases with the increase of the thickness of sediment. Surface of10~20cmthick column-like K is the largest, the middle of30~50cm thick column-like K values ranged smaller and more stable.Riverbed K values presented lognormal distributionwith depth, the variation coefficient value is1.039>1, as the strong variability;Riverbed sediments of permeability coefficient K value with sediment thickness obeys lognormal distribution, the variation coefficient value is1.013>1, which presented strongvariability;the range of streambed hydraulic conductivity K vary with depth is27cm,spatial correlation is9.94%, showing a strong spatial correlation. K changing with thedepth is affected by sediment lithology. The sediment grain size decrease with depth,K value and the d60is the most relevant, the fitting degree is0.86, K=10.47d602.Ⅱ:Spatial variability of streambed hydraulic conductivity on typical cross sectionRiverbed sediment permeability coefficient values decreasing from both sides of the bed to the center, the degree of variation of transverse secation is greater than thecross section of the longitudinal section. ⅰ: In the upstream diluvial sector, riverbed sediment permeability coefficient values are obvious mutation along cross section and longitudinal section. The average K of longitudinal section is68.62m/d, cross section average of18.78m/d, the overall changes between0.75~233m/d.Controlled by lithology conditions, upstream burst diluvial sector particle size size disparity, sorting and uniformity is very poor, K obeys lognormal distribution.The variation coefficient>1, presented strong variability.Variation function calculation results show that the range of the stream profile K is4m, spatial correlation is0.8%, was strongly related; the range of cross section is15m, spatial correlation was29%, was medium variability.ⅱ:In the downstream fine soil plain, riverbed sediment permeability coefficient ofhorizontal longitudinal section of the river bed changes more obvious, and almost constant along the longitudinal profile.Longitudinal section of K-means is19.12m/d, crosssection of K-means is13.93/d, the overall change between0.65to47.37m/d. The sediment particle uniformity is good, the differences of K is not very large, obey the normal distribution, the variation coefficient between0.1~1, showed medium variability.Variation function calculation results show that the range of the stream profile K is22.25m, spatial correlation was50%, was medium variability; the range of cross sectionis27m, spatial correlation is5.7%, was strongly related.ⅲ:Typical profile riverbed sediments value K is mainly affected by river morphology,flow, undercurrent with hydrological processes and sediment lithology effects. The resultsshowed that due to the difference of sediment particle separation, the diluvial sector sedimentK value was most related to characteristics of grain size d30, in which the relation is:logK=4.1752*0.5598logd30. Fine soil plain sediment has a good uniformity, there is a linearcorrelation between particle size d102and K, in which the K relation is: K=2021.8*d102. Kdecreases with the increase of Cu, when the uniformity coefficient is greater than5and bothare independent, when less than5.Ⅲ:Spatial variability of streambed hydraulic conductivity on catchment scaleRiverbed sediment permeability coefficient values flow down along the river basin scaleshowing an overall downward trend, the average riverbed sediments K is42.587m/d frommountain pass to stream outlet, changes between8.390~98.570m/d, which obeyed lognormaldistribution,the coefficient of variation is0.743,was moderate variability. The maximumlength of the space under the relevant river basin scale sediment permeability coefficientvalue is about15km, the spatial correlation is8.18%<25%, the spatial correlation is very strong. The optimal fitting model is spherical model under LnK, and Co is greater than0,indicating that the area is poor spatial continuity, space variable difference is obvious.Basin-scale permeability is mainly affected by river sediment conditions, geographic andgeomorphic conditions, hydrodynamic condition and sediment lithology. Multiple linearregression analysis and principal component analysis get a K expression which is through themain ingredient.The research on the Golmud River riverbed sediment permeability coefficient involves a lot of experimental studies, and preliminarily elicits the riverbed sediment permeability distribution space, quantitatively studied the spatial variability of the value ofK under different scales, in-depth analyzed the factors affecting changes in the value of K, initially established a relationship expression of K with the size, provides a reliable parameter of translational research relationship on Golmud River surface water andgroundwater.