| Hyporheic zone is the area for stream and groundwater to exchange their mass and energy Hyporheic exchange has important impacts on water quality and ecological health for them.Based on the classic EB model,this work studies the effect of regional groundwater,anisotropy of hyporheic zone,fluctuation of water level in river and movement of the dunes on hyporheic exchange through theoretical analysis(the hyporheic flow induced by the movement of river bed dunes is called turnover).The results show that:1.The recharge and discharge flows of regional groundwater affect the mixing depth of upwelling and downwelling in hyporheic zone,the parameters of the transient storage model for simulating the water quality of river should take into account the effects of regional groundwater recharge and discharge;2.With the increase of the ratio between longitudinal and latitudinal permeability coefficient,hyporheic exchange increases,the average residence time shorter,mass exchange increases;3.In the case of unsteady pumping flow cased by the fluctuation of water level,with the increase of the fluctuation frequency of water level,the hyporheic flow field is more disturbed,hypoheic exchange increases,the average residence time is shorter,mass exchange increases;with the decrease of pressure conduction coefficient,hyporheic exchange increases first and then decreases,the average residence time is longer,mass exchange increases first and then decreases;4.In the case of unsteady turnover flow cased by the movement of riverbed dunes,with the increase of the moving velocity of riverbed dunes,the hyporheic flow field is more disturbed,the average residence time is shorter,mass exchange decreases;with the decrease of pressure conduction coefficient,hyporheic exchange decreases first and then does not change,the average residence time is shorter,mass exchange decreases.In these two cases of unsteady hyporheic flow,the flow field is not affected finally by pressure conduction coefficient when it becomes larger. |
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