Measurement of streambed hydraulic conductivity and anisotropy analysis

The hydraulic conductivity between stream and adjacent aquifers is an important issue for water resource management.The hydraulic conductivity of the streambed is an essential variable in determining the hydraulic connection between a stream and adjoining aquifers.The paper applies straight and L-shaped standpipes directly to streambeds for measuring the in-situ hydraulic conductivity in the vertical(k_v) and horizontal(k_h) directions,as well as in other oblique directions(k_s) in the middle reaches of Heihe river.Results indicate that the hydraulic conductivity of streambed has not only significant anisotropy,but also variability at the spatial scale.In the same measured spot,the hydraulic conductivity decreases with the increase of the angle between horizontal and measurea direction(θ).At the spatial scale,the hydraulic conductivity of side streambed is higher than that of the middle streambed,especially in the vertical direction This indicates that the side streambed is an important leakage region.