Abstract: Hyporheic exchange has significant impact on the changes of water quantity in the hyporheic zone and residence time of various substances (oxygen and organic matters). Accurate calculation of hyporheic exchange flux and its dynamic change is of crucial importance for the integrated management and ecological restoration of rivers. In the present paper, the hyporheic flux in the hyporheic zone of the Caotan section of Weihe River is calculated by using heat transfer model as a case study. The spatial heterogeneity and dynamic change of hyporheic exchange are examined through temperature tracing. Results show that in the monitoring period, groundwater in the study area was recharged by river flow. Hyporheic flux varied in a range of 8.73×10^-7-8.90×10^-6m/s in shallow hyporheic zones of about 0.75 m thick at different locations, displaying complex dynamic feature. In the monitoring period, the overall trend of hyporheic flux at different depths was increasing, yet with some differences in vertical distribution varying with time. The results prove that temperature tracing method is simple and accurate in the calculation of hyporheic flux, and is suitable for the calculation of hydrodynamic exchange capacity in hyporheic zone.

Key words: hyporheic zone, hyporheic flux, heat, tracer, Weihe River