An international laboratory flume manufacturer, Armfield Engineering Teaching and Research of Ringwood England, has blogged (read it and watch the video!) about our recent research discovery. We used our C4 Armfield flume in a non-traditional experimental setup: adding a 10 cm layer of pebbles, creating rapidly varied and gradually varied flows (i.e., the water surface curved between two different depths) in the surface water above the pebbles, and then injecting blue dye into the pebble zone called the hyporheic zone. What we observed next was a water feedback loop, where variation in surface water velocities established a pressure field around the hyporheic zone that pushed hyporheic water up river! The river water was caught within a recirculating eddie around a horizontal axis, moving between the pebble medium and the open water medium. The feedback structure provides important ecosystem functions, delivering a steady supply of nutrients from the surface water to the subsurface micro-biological community, which then provides a food source for the larger aquatic organisms, from macro-invertebrates to fish. We are getting the word out on this important ecosystem function with a video for river restoration engineers (so they can consider ways to use structures that encourage these natural processes) and with a journal articlefor the science and engineering research teams. You may notice another feedback loop: our ERE blog is feeding to Armfield’s blog which is feeding to ERE…

Surface flow moving to the left + Subsurface flow moving to the right = Feedback Loop

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