A Multiple-Segment Recirculating Flume to Quantify Chemical Transport Processes in Drainage Ditches.

Recirculating flumes have been used to quantify chemical transport between the soil (or sediment) and the flowing water.  Some researchers used recirculating flumes to simulate chemical transport processes occurring in flowing streams or drainage ditches.   When we examined the theoretical basis of the recirculating flume experiments, we found that the sediments in a fixed length flume behave like a point source or sink for chemicals and it is a challenge to extend results from a point to a stream reach.   To provide a more realistic simulation of chemical transport processes, we designed a multiple-segment recirculating flume that consist of four 5-meter long individual flumes that are connected and can be sampled in between any of the segments, i.e., a 20-m long segmented flume.  We also installed water supply or drainage lines to control the hydraulic gradient at channel bottom to simulate sub-surface hydrologic processes occurring at the hyporheic zone.   In this presentation, we will present the analytic basis of the multiple-segment flume and show results from initial runs made in this flume.