Assessing groundwater travel times and biogeochemical processes during riverbank filtration under the aspect of river restoration

摘要

The largest Swiss groundwater reservoirs are located in gravel aquifers of flood plains with channelized rivers. Although the number of river restoration projects is increasing, the effects of river restoration on riverbank filtration and groundwater quality are still under debate. For detailed research on biogeochemical processes during river water infiltration, field data of nutrients or pollutants and advective groundwater travel times to observation and production wells are crucial parameters. We present results of a study on bank filtration at a field site in northeast Switzerland, which is located at a channelized and restored section of the peri-alpine losing River Thur. We analyse time series of electrical conductivity in the river and riparian ground-water wells to quantify mean residence times by means of non-parametric deconvolution and relate the calculated travel times with biogeochemical processes occurring during riverbank filtration.