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Mixing and exchange processes between two estuaries in Stockholm Archipelago, Sweden
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering.
2008 (English)In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015Article in journal (Other academic) Submitted
Abstract [en]

ECOM, a three-dimensional time dependant hydrodynamic and thermodynamic model, was used to investigate the mixing and exchange processes between Farstaviken and Baggensfjärden estu-aries in Stockholm archipelago during April to November 1997. Possible causes of bottom oxy-gen deficiency in the smaller estuary of Farstaviken were also investigated. The model with an additional boundary condition for the sediment-water heat exchange and modifications to reduce the pressure gradient error successfully produced the observed temperature profiles by allowing a time variable reduction in the magnitude of the observed wind speed. In Farstaviken (during stratification periods) the epilimnion region occupies 2.5%-17.5% of the flow depth. The ex-change process between the two smaller and larger estuaries is different from that observed be-tween larger basins where density driven currents dominate. Here, the process is primarily con-trolled by wind action and tides. On average 5% of the total water volume of Farstaviken is exchanged with Baggensfjärden on daily basis. The bottom oxygen deficiency in Farstaviken during April to November 1997 is partially related to the topography of the basin and the wind sheltering effect. To investigate this issue as well as the sensitivity of mixing to the changes in topography, additional simulations were performed using a modified bathymetry. The original bathymetry was smoothed using the 2D Gaussian filter. The results showed that both the intensi-ties and penetration depths of eddies were increased in comparison with the original bathymetry. The enhanced circulation can also contribute to increase the content of dissolved oxygen near the bottom of Farstaviken.

Place, publisher, year, edition, pages
2008.
Keyword [en]
Mixing and flow exchange, Three-dimensional modeling, Wind sheltering, Basin bathymetry, Bottom oxygen deficiency
National Category
Water Engineering
Identifiers
URN: urn:nbn:se:kth:diva-8248OAI: oai:DiVA.org:kth-8248DiVA: diva2:13519
Note
QS 20120315Available from: 2008-04-22 Created: 2008-04-22 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Modeling flow and sediment transport in water bodies and watersheds
Open this publication in new window or tab >>Modeling flow and sediment transport in water bodies and watersheds
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The research focus is on the various modeling aspects of flow and sediment transport in water bodies and watersheds. The interaction of flow with a mobile bed involves a complex process in which various turbulent scales characterized by coherent structures cause a chaotic sediment motion. In many rivers and natural waterways secondary flows that are dominating flow struc-tures bring about more complications. In estuaries and open waterbodies thermal stratification and internal mixing control the flow structure besides the flow interaction with the mobile bed. To adequately model these processes 3D coupled flow and transport models are needed. The research is based on use and adaptation of open source codes for 3D hydrodynamic and sediment transport model known as Estuarine Coastal Ocean Model (ECOMSED) and the Soil and Water Assessment Tool (SWAT) model. A bed load transport model was developed and coupled to ECOMSED. The flow and sediment transport characteristics in a curved channel and a river reach were successfully captured by the model. Improvements in ECOMSED were made to study the effect of wind and basin bathymetry on mixing and flow exchange between two estuaries. Using spectral analysis the hydrological component of SWAT model was investigated for its applicability under limited data conditions in three Ethiopian catchments.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. viii, 21 p.
Series
Trita-LWR. PHD, ISSN 1650-8602 ; 1039
Keyword
Bed load transport model, ECOMSED, Hydrology, Hydrodynamics, Spectral Analysis, SWAT
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-4703 (URN)978-91-7178-925-9 (ISBN)
Public defence
2008-05-08, F3, Lindstedtvägen 26, Kungliga Tekniska högskolan | Adress SE-100 44 Stockholm | Telefon +46 8 790 60 00, KTH, 10:00
Opponent
Supervisors
Note
QC 20100827Available from: 2008-04-22 Created: 2008-04-22 Last updated: 2010-08-27Bibliographically approved

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