『Summary
A simple thermal mapping method for simulating seasonal and spatial
patterns of groundwater-surface water interaction is developed
and tested for a segment of the Aa River, Belgium. Spatially distributed
temperature profiles in the hyporheic zone of the river are measured
in winter and summer seasons of three consecutive years. Inverse
modeling of the one-dimensional heat transport equation is applied
to estimate vertical advective fluxes using the numerical STRIVE
model and an analytical model. Results of the study show that
seasonal flux estimates for summer and winter can be derived with
a minimum data input and simulation effort. The estimated fluxes
are analyzed via non-parametric statistical tests, while spatial
interpolation techniques are used to generate maps of distributed
flux exchange. The estimated seepage is compared with volumetric
flux obtained from piezometer measurements and output of a groundwater
model. The thermal method shows higher discharge rates in winter
and that the relative contribution of exfiltration on the river
discharge is higher in summer. A higher flux and a more heterogeneous
flow pattern are observed in the upper reach of the river compared
to the lower reach. This spatial difference shows the importance
of the local geomorphology and to a lesser extent the hydrogeologic
setting on hyporheic flux exchange in the river. A significantly
higher flux is noted on the banks than in the center of the river,
which is driven by the relatively high hydraulic conductivity
of the river banks. It is concluded that bank flow in groundwater-surface
water interaction deserves more attention. The main channel of
the Aa River alone accounts for about 15％ of the total river discharge
at its outlet. As the developed thermal method is cost-effective,
simple and fast, it is recommended for use in identifying zones
o interest in initial stages of field investigations of groundwater-surface
water interaction.
Keywords: Heat transport modeling; Temperature; Hyporheic zone;
Groundwater-surface water interaction; FEMME; Belgium』
1. Introduction
2. Methodology
2.1. Arriaga and Leap (2006) model
2.2. STRIVE model
3. Field site and measurements
4. Results and discussion
4.1. Spatial patterns
4.2. Seasonal differences
4.3. Net flows
5. Conclusions
Acknowledgements
References