THE APPLICATION OF HEAT AS A NATURAL TRACER OF HYPORHEIC FLOW IN RED CANYON CREEK

Naturally occurring diurnal temperature fluctuations in streambeds can identify the nature of hyporheic interaction. We used inexpensive iButton data loggers to make frequent, accurate temperature observations at various depths in the streambed in Red Canyon Creek, Wind River Range (WY) and to evaluate hyporheic interaction during base flow conditions. Red Canyon Creek watershed contains numerous beaver dams and meanders, which should enhance hyporheic interaction in this semi-arid climate.

iButtons were inserted into wooden dowels which were driven into the streambed to record temperatures of the stream and sediments at 5, 15, and 25 cm depths. The iButtons recorded temperature to an accuracy of about 0.07 degrees Celsius for 1.5-hour intervals from 7/11/05 to 10/14/05. Diurnal temperature patterns occurred at all depths, and peak temperature variations for each depth lagged behind peak stream temperatures. The maximum lag times observed ranged from 4 to 12 hours across the vertical profiles, and occurred most notably at 25cm depth.

The hydraulic conductivity of the streambed sediments and the hydraulic gradient across the profiles controlled the lag time in temperatures. We used the U.S. Geological Survey's heat and ground water transport model (VS2DH) to create one-dimensional simulations of the vertical temperature profiles. Results from these simulations show a high degree of sensitivity to streambed hydraulic conductivity (K) and suggest that temperature measurements can be used to accurately refine measured K values for streambed sediments in this stream. The amplitude of the temperature fluctuations in the streambed directly relate to vertical head differences in mini-piezometers showing where stream reaches gain or lose water. Larger amplitudes are observed where stream water recharges to the ground, and more consistent, smaller amplitudes are observed where groundwater discharges to the stream.