A heat pulse technique for the determination of small‐scale flow directions and flow velocities in the streambed of sand‐bed streams |
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| Authors: | Jörg Lewandowski Lisa Angermann Gunnar Nützmann Jan H Fleckenstein |
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| Institution: | 1. Department Ecohydrology, Leibniz‐Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, D‐12587 Berlin, Germany;2. Department of Hydrology, University of Bayreuth, Universit?tsstr 30, D‐95440 Bayreuth, Germany;3. Department Hydrogeology, Helmholtz Center for Environmental Research (UFZ), Leipzig, Germany |
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| Abstract: | The hyporheic zone (HZ) has the capability to eliminate and attenuate nutrients and contaminants in riverine systems. Biogeochemical reactions and the potential elimination of contaminants are strongly controlled by the flow paths and dynamics in the HZ. Nevertheless, an easily applicable method for the field determination of flow patterns in the HZ is still lacking. Therefore, a heat pulse technique, which traces the movement of a short heat pulse in the upper part of the HZ and other sand beds, was developed. Five rods are vertically driven into the sediment of the streambed; one rod with a heater as point source located in about 10‐cm sediment depth and four rods with four temperature sensors in 3 cm distance, arranged concentrically with 7 cm diameter around the heating rod. Subsequently, a heat pulse is applied and the resulting breakthrough curves are indicative of flow velocities and flow directions in the streambed. A rough data analysis procedure is also suggested. In addition, laboratory experiments were performed to test the heat pulse technique. These experiments were validated based on coupled numerical modelling of flow and heat transport. First field tests of the method prove that the method is easily applicable under field conditions. These first field tests showed highly complex flow patterns with flow velocities from 1·8 to 4·9 cm min?1 and flow directions from parallel to surface flow to opposite to surface flow. This suggests the need for a robust method to quantify hyporheic flow patterns in situ. Copyright © 2011 John Wiley & Sons, Ltd. |
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| Keywords: | flow direction flow velocity hyporheic zone sandy beds heat pulse technique |
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