| Abstract |
- Temperature anomalies can identify locations of seeps of groundwater into surface waters.
However, the method’s sensitivity to details such as thermometer burial depth, sediment material, seep
velocity, and surface water current are largely unknown. We report on a series of laboratory flume experiments
in which controlled seeps under variable sediment texture, surface currents, burial depth, and temperature
differentials were imposed. The focus of the study is temperature effects at the sediment surface
to a few centimeters below the sediment surface, as these locations are of particular interest when using
fiber-optic distributed temperature sensors (DTS). The data demonstrate: (1) without surface water flow,
seep-related thermal anomalies were apparent in all cases, i.e., the method is feasible in such cases; (2)
probe burial is helpful for fine sediment although not effective with coarse bed sediment, i.e., the method is
strongly sensitive to sediment properties; (3) placing a thin rubber sheet over an unburied thermal probe
increases detection of seeps in some circumstances, but not in others, and is generally not as robust as
probe burial; and (4) local surface flow velocity, details of probe position and depth, and seepage velocity
all influence observed temperature anomalies, limiting the opportunity to quantify seepage velocity, particularly
with unburied temperature sensors. Overall, these findings suggest optimal installation would be at a
well-defined depth within fine sediment, that installation in gravel and coarser sediment is not suited to the
method if there are any significant surface currents, and that more data would be required to obtain accurate
estimates of seepage velocity, though a single sensor may be sufficient to identify the location of
seepage.
- Keywords: Seepage, Gravel, Temperature, Sediment, Sand, Flow
- Keywords: Seepage, Gravel, Temperature, Sediment, Sand, Flow
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