Factors controlling riffle-scale hyporheic exchange flows and their seasonal changes in a gaining stream: A three-dimensional groundwater flow model

被引:254
作者
Storey, RG
Howard, KWF
Williams, DD
机构
[1] Univ Toronto, Div Life Sci, Scarborough, ON M1C 1A4, Canada
[2] Univ Toronto, Div Phys Sci, Scarborough, ON M1C 1A4, Canada
关键词
hyporheic zone; groundwater-surface water interactions; modeling; MODFLOW;
D O I
10.1029/2002WR001367
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
[1] Subsurface flow within a single riffle of a low-gradient gravel bed stream was modeled in three dimensions using MODFLOW, a finite difference groundwater flow model. Model simulations showed that exchange flows can only occur in this low-gradient, gaining stream because of a zone of alluvial sediment around the stream that has much higher permeability than the surrounding catchment (K = 10(-4) m s(-1), compared with K = 10(-6) to 10(-8) m s(-1)). The key factors controlling exchange flow within the alluvial zone were identified as the hydraulic conductivity of the alluvium, the hydraulic gradient between upstream and downstream ends of the riffle, and the flux of groundwater entering the alluvium from the sides and beneath. In the study riffle each of these factors changes with season, causing a reversal of flow paths in the alluvium and a reduction in exchange flows from about 0.2 - 0.5 m(3) d(-1) per meter stream length in summer to about 0.008-0.04 m(3) d(-1) per meter stream length during fall to spring. The model also revealed that exchange flows are up to twice as strong, but more variable, at the sides of the stream than near the center, and that vertical flow paths beneath the channel are more persistent under the range of conditions modeled than lateral flow paths into the banks.
引用
收藏
页码:SBH81 / SBH817
页数:17
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