Ground-Penetrating Radar Hyporheic Project
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Ground-Penetrating Radar Hyporheic Project |
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| Overview: We
are investigating the potential to use ground-penetrating radar
techniques (multi-offset data acquisition, cross borehole tomography)
to detect stream ionic tracers (dissolved salt) in the hyporheic zones
of mountain streams. Specifically, our field sites are in the Sawtooth
Mountains of Idaho. As a proof-of-concept project, we expect that the exchange of salt-labelled stream water into the hyporheic zone will modify the dielectric properties of hyporheic water enough to be detectable with GPR and resistivity measurements. At right is an image of the inflow delta of Springs Cr. into Bull Trout Lake. |
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 After choosing our site, a tall dune bounded by pools, we had to install boreholes to 2m depth. |
 Our completed transect #2 (looking downstream) consisted of 3 boreholes and 2 piezometer sets. Piezometers are white pvc tubes at depths of ~20cm and ~40cm. The dark spot in the foreground is organic litter collected in the pool upstream of the dune. Transect #1 was set up across the pool just upstream of Tranect #2 seen here. |
 Transect #3 was completed with piezometers only, no boreholes. Transect #4, over a pool, is in the background. Note the pool in the foreground, dune at Transect #3, and pool in the background. |
 We also made resistivity measurements in the subsurface during the stream tracer experiments. Note that we co-injected dissolved NaCl and rhodamine WT dye. Also note Transect #1 at the upstream (foreground) wooden plank. |
 In order to achieve our target increase of specific conductance in the stream of 100 uS/cm, we had to use 2 injection pumps. Mixing in the downstream bend and subsequent pool was efficient. |
 Transect #1 (left) and #2 (right) during the experiment. The green wires are used for subsurface resistivity measurements. |
 Kristen working with the cross-borehole equipment. |
 John works the borehole on the opposite bank. |
| Click on this link for pictures from our
first field campaign in late September 2007. |
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Current
Weather at Banner Summit, ID
(from the National Weather Service in Pocatello, ID) |
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This project is
funded through the United States Department of Agriculture's National
Research Initiative.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the USDA. |