Hydraulic conductivity is of importance to the hydraulic connection between surface water and groundwater and the water quantity exchange in hydraulic zone.The composition and content of organic and inorganic compounds in sediment may affect the hydraulic connection.The vertical hydraulic conductivity(K)for a streambed was measured by falling-head standpipe permeameter tests conducted in the four sites of Xianyang City

Caotan and Lintong area of Xi'an City

and Huaxian County in the lower reaches of the Weihe River in Shaanxi Province.The K.

values were between 0.02 and 61.32 m/d

with an average value of 5.13 m/d. Spatial distribution of sediment hydraulic conductivity indicates that the Kr

value was the highest in Caotan area and then in Lintong area.The Kr

values in Huaxian County and Xianyang City were relatively low and in Huaxian County

the lowest.Analysis of the correlations between the Kr

value and sediment physiochemical properties was made using Pearson coefficient method. Among the sediment physiochemical indexes

manganese

total phosphorus and ferrous ion were found to be the main factors affecting streambed hydraulic conductivity and the effect increased with the increased hydraulic conductivity.