Abstract:

Temperature time-series records were used to determine groundwater-surface water (GW-SW) exchange. If it is assumed that the temperature on the top boundary is oscillated in a sinusoidal pattern, the analytic model to calculate the seepage velocity by temperature damping can be obtained. Two typical analytic solutions are Hatch solution and Keery solution. The study shows that the Hatch solution is more accurate due to taking thermal diffusion into account. So it’s recommended that Hatch solution should be adopted to calculate seepage velocity. A typical permeable medium is taken as a case, and limitations and applicability of the model were discussed. It is shown that only when the study area can be simplified as a homogeneous medium and vertical seepage is dominant, the analytic model can be used. For the common interval of test points (around 1.0 m), it’s more effective to compute seepage velocity from -1.0×10^-5 m/s to 8.0×10^-5 m/s by using amplitude damping method and from 0.0 m/s to 1.6×10^-4 m/s by using phase lagging method, respectively. For the analytic model, the two test points must have amplitude damping and phase lagging. So the seepage velocity in the domain should be estimated firstly, and the reasonable interval of test points be designed then. It is shown from a case study that this method is available for evaluating the temporal variation of GW-SW exchange.

Key words: groundwater-surface water exchange, seepage velocity, temperature, time-series record, analytic model