Preliminary Testing of a Streambed PVP, and its Application to Groundwater-Surface Water Interactions in a Stream in Jutland, Denmark

Monday, October 5, 2015
Mackenzie Cremeans and John F Devlin, University of Kansas, Lawrence, KS, United States
Preliminary testing of a streambed PVP, and its application to groundwater-surface water interactions in a stream in Jutland, Denmark

by M. Cremeans and J.F. Devlin

Geology Dept., University of Kansas

Point velocity probes (PVPs) measure in situ groundwater velocities by performing a mini-tracer test on the probe surface. They are capable of measuring groundwater speed and direction without the need for hydraulic conductivity or gradient information. Prior research has demonstrated the viability of PVPs in sand aquifers, a glacial outwash aquifer, and along a stream bank. In this work, the PVP design was modified to make it suitable for use near the top of a streambed, to provide direct measurements of water flow upward into the stream. The objectives of the study included the testing and application of the streambed PVP, and its use in conjunction with the original PVPs installed in the stream banks, to characterize groundwater-stream water interactions, and to provide a means of characterizing streambed heterogeneity. The new instrument was laboratory tested with promising results, and then field tested in the bed of the Grindsted Å (stream) in Jutland, Denmark. To assess the performance of the streambed PVP, comparisons with concurrently gathered data from conventional methods, such as Darcy’s Law calculations, temperature gradients, and seepage meters, were performed. Preliminary results suggest promising agreement across the methods, suggesting the streambed PVP device was performing satisfactorily. Preliminary analysis of the data suggests that the Grindsted Å streambed is strongly heterogeneous with zones of no measureable upward flow within a meter of zones of high upward flow along a given transect (line perpendicular to the stream flow direction). In the Grindsted Å, a high flow zone in one transect was responsible for most of a plume of vinyl chloride, identified in previous work by others, that persisted in measurable concentrations that persisted in the stream water over a reach tens of meters long.