Revisiting the modified Hvorslev formula to account for the dynamic process of streambed clogging: Field validation

Abstract

Estimating streambed hydraulic conductivity is particularly important in arid and semi-arid regions, where surface water infiltration from ephemeral dryland streams helps maintain riparian ecosystems. In situ permeameter tests are widely used to estimate the hydraulic conductivity of streambed sediments. Previous studies have demonstrated that one of the major factors controlling spatiotemporal variations in streambed hydraulic conductivity in such areas is streambed clogging by suspended sediments. Recently, a modified Hvorslev (1951) formula was theoretically proposed to account for the effect of streambed clogging on streambed hydraulic properties due to suspended particle sedimentation during falling-head tests. To validate the modified formula, fieldwork was conducted at five sites in the lower Heihe River, a typical intermittent river of north-western China, in September 2017. A simple PVC pipe with an inner diameter of 4 cm was used as a permeameter for the field tests. Both muddy river water and clean water were used to fill the permeameter to conduct comparative tests. To differentiate the interpretation of the field testing data obtained with clean water, the data obtained with muddy river water were analysed with an equation considering an iteratively increasing total hydraulic resistance of riverbed sediments due to the effects of riverbed clogging. The estimated vertical hydraulic conductivity for the top 0.3 m of riverbed sediments varied from 1 to 41 m/day. The proposed model was shown to accurately estimate the hydraulic conductivity of riverbed sediments using both clean and muddy water during slug tests.