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Investigation of the Effect of Multi...

Stonedahl, Susa Hardwick.

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Investigation of the Effect of Multiple Scales of Topography on Hyporheic Exchange.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Investigation of the Effect of Multiple Scales of Topography on Hyporheic Exchange./
作者:	Stonedahl, Susa Hardwick.
面頁冊數:	215 p.
附註:	Source: Dissertation Abstracts International, Volume: 72-08, Section: B, page: 4517.
Contained By:	Dissertation Abstracts International72-08B.
標題:	Hydrology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3456705
ISBN:	9781124662947

Investigation of the Effect of Multiple Scales of Topography on Hyporheic Exchange.
Stonedahl, Susa Hardwick.

Investigation of the Effect of Multiple Scales of Topography on Hyporheic Exchange. - 215 p.

Source: Dissertation Abstracts International, Volume: 72-08, Section: B, page: 4517.

Thesis (Ph.D.)--Northwestern University, 2011.

Water and waterborne solutes continuously exchange with the surrounding sediments. This process is termed hyporheic exchange. The sediments surrounding the stream are rich with biological activity, which can transform solutes carried in the water. The amount of transformation that takes place is related to the amount of time the water spends in the sediments, the composition of the sediments, and the biological communities present. In this work I investigated the hydrodynamic and geomorphic controls on exchange flow and subsurface residence time distributions. I developed a physically based multi-scale model for the relationship between stream topography and hyporheic exchange. The model predicts the hyporheic flow paths based on a priori system characteristics such as stream discharge, hydraulic conductivity, and valley slope, as well as stream channel topography of the system. From this model we get residence time distributions for water in the subsurface as well as spatially distributed estimates of the interfacial flux of water into and out of the subsurface. The model uses a Schwarz-Christoffel conformal mapping of the stream planform to align the topography with the direction of flow. Then it approximates a function for head variation based on stream topography and surface water flow variation using Fourier series and finite difference calculations. I have applied the model to two stream topographies generated in laboratory flumes, a small, ditched agricultural stream, and multiple idealized meandering stream channel planforms. Two simulations were compared with empirical datasets. The solute data compared favorably for a laboratory flume simulation as did the natural system for the longer exchange time scales. The discrepancy at short exchange time scales indicates that the tracer data characterized shorter exchange times than those captured by our model. The simulations demonstrated that all scales of topographic features contribute to interfacial flux and residence time distributions, but that ripple and dune scales tend to both contribute more than and interact nonlinearly with meanders. Simulations of the natural stream showed that groundwater input shortened hyporheic residence times and both confined the flux into the subsurface to the center of the stream and decreased the total amount of water entering the subsurface.

ISBN: 9781124662947Subjects--Topical Terms:

545716
Hydrology.

Investigation of the Effect of Multiple Scales of Topography on Hyporheic Exchange.
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