Salt transport on islands in the Okavango Delta: Numerical investigations

This study uses a numerical model to investigate the groundwater flow and salt transport mechanisms below islands in the Okavango Delta. Continuous evapotranspiration on the islands results in accumulation of solutes and the formation of a saline boundary layer, which may eventually become unstable....

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Bibliographic Details
Published in:Advances in water resources 2006, Vol.29 (1), p.11-29
Main Authors: Zimmermann, S., Bauer, P., Held, R., Kinzelbach, W., Walther, J.H.
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
aquifers
Biological and medical sciences
deltas
Density-driven groundwater flow
Earth sciences
Earth, ocean, space
Exact sciences and technology
Free convection
Fundamental and applied biological sciences. Psychology
groundwater flow
Hydrogeology
hydrologic models
Hydrology. Hydrogeology
inorganic salts
islands
mathematical models
Numerical study
Particle methods
Saline boundary layer
saline water
soil transport processes
solutes
Synecology
Terrestrial ecosystems
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Summary:This study uses a numerical model to investigate the groundwater flow and salt transport mechanisms below islands in the Okavango Delta. Continuous evapotranspiration on the islands results in accumulation of solutes and the formation of a saline boundary layer, which may eventually become unstable. A novel Lagrangian method is employed in this study and compared to other numerical methods. The numerical results support the geophysical observations of density fingering on Thata Island. However, the process is slow and it takes some hundreds of years until density fingering is triggered. The results are sensitive to changes of the hydraulic gradient and the evapotranspiration rate. Small changes may lead to different plume developments. Results further demonstrate that density effects may be entirely overridden by lateral flow on islands embedded in a sufficiently high regional hydraulic gradient.
ISSN:0309-1708
1872-9657
DOI:10.1016/j.advwatres.2005.04.013