Salt transport on islands in the Okavango Delta: Numerical investigations |
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Authors: | S Zimmermann P Bauer R Held W Kinzelbach JH Walther |
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Institution: | 1. Institute of Hydromechanics and Water Resources Management (IHW), ETH Hönggerberg, Zürich CH-8093, Switzerland;2. Institute of Computational Sciences (ICOS), ETH, Zürich CH-8092, Switzerland |
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Abstract: | 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. |
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Keywords: | Saline boundary layer Free convection Density-driven groundwater flow Numerical study Particle methods |
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