| 1. |
- Paul, Seema, et al.
(författare)
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A shallow water numerical method for assessing impacts of hydrodynamics and nutrient transport processes on water quality values of Lake Victoria
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Lake Victoria is the world’s largest tropical lake and the third-largest water body, providing significant water resources for surrounding environments including the cultural, societal, and livelihood needs of people in its basin and along the White Nile. The aim of this study was to use decade-long time series of measured lake flow in the lake system and phosphorus deposition to develop a suitable numerical model based on shallow water equations (SWE) for assessing water quality in Lake Victoria, an increasingly important tool under climate variation. Different techniques were combined to identify a numerical model that included: i) a high-resolution SWE model to establish raindrop diffusion to trace pollutants; ii) a two-dimensional (2D) vertically integrated SWE model to establish lake surface flow and vertically transported wind speed flow acting on lake surface water by wind stress; and iii) a site-specific phosphorus deposition sub-model to calculate atmospheric deposition in the lake. A smooth (non-oscillatory) solution was obtained by applying a high-resolution scheme for a raindrop diffusion model. Analysis with the vertically integrated SWE model generated depth averages for flow velocity and associated changes in water level profile in the lake system and showed unidirectional whole lake wind blowing from the southwest to northeast. The atmospheric phosphorous deposition model enabled water value assessment for mass balances with different magnitudes of both inflows and outflows demonstrating annual total phosphorus at 13,500 tons concentrating at mid-lake western and eastern parts. The model developed here is simple and suitable for use in assessing flow changes and lake level changes and can serve as a tool in studies of lake bathymetry and nutrient and pollution transport processes. Our study opens towards refining models of complex shallow-water systems.
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| 2. |
- Paul, Seema, et al.
(författare)
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A shallow water numerical method for assessing impacts of hydrodynamics and nutrient transport processes on water quality values of Lake Victoria
- 2024
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Lake Victoria is the world’s largest tropical lake and the third-largest water body, providingsignificant water resources for surrounding environments including the cultural, societal, andlivelihood needs of people in its basin and along the White Nile. The aim of this study was to usedecade-long time series of measured lake flow in the lake system and phosphorus deposition todevelop a suitable numerical model based on shallow water equations (SWE) for assessing waterquality in Lake Victoria, an increasingly important tool under climate variation. Different tech-niques were combined to identify a numerical model that included: i) a high-resolution SWEmodel to establish raindrop diffusion to trace pollutants; ii) a two-dimensional (2D) verticallyintegrated SWE model to establish lake surface flow and vertically transported wind speed flowacting on lake surface water by wind stress; and iii) a site-specific phosphorus deposition sub-model to calculate atmospheric deposition in the lake. A smooth (non-oscillatory) solution wasobtained by applying a high-resolution scheme for a raindrop diffusion model. Analysis with thevertically integrated SWE model generated depth averages for flow velocity and associatedchanges in water level profile in the lake system and showed unidirectional whole lake windblowing from the southwest to northeast. The atmospheric phosphorous deposition modelenabled water value assessment for mass balances with different magnitudes of both inflows andoutflows demonstrating annual total phosphorus at 13, 500 tons concentrating at mid-lakewestern and eastern parts. The model developed here is simple and suitable for use in assess-ing flow changes and lake level changes and can serve as a tool in studies of lake bathymetry andnutrient and pollution transport processes. Our study opens towards refining models of complexshallow-water systems
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| 3. |
- Watts, Hannah, 1994-
(författare)
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Exploring beneath the surface of glacial landscapes : Implementing and improving geophysical investigations in glaciated environments
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The warming climate is having profound impacts on glacier dynamics and extents. To improve our predictions of future ice mass changes, we require an enhanced understanding of both past and present glacial processes. The physical properties and structure of glacial sediments and landforms aid reconstructions of past environments and ice dynamics on numerous scales. Traditionally, these factors have been studied using glacial geological techniques such as sedimentary logging. While this provides valuable in situ data, there are numerous limitations, namely the limited availability and spatial extent of exposures. In recent decades, near-surface geophysical techniques have gained in popularity within the fields of glaciology, geomorphology, and sedimentology. Geophysics offers a non-invasive means of obtaining spatially extensive data on substrate properties and architecture, however issues such as signal scattering and interpretation ambiguity in complex glaciated environments restrict its application.This thesis exemplifies how near-surface geophysical techniques can aid glacial landscape interpretations focusing on ground-penetrating radar, seismic refraction, and multi-channel analysis of surface waves. It explores the current limitations of the methods and outlines solutions to improve their applicability, in terms of geophysical campaign success, as well as uncertainty estimation and visualisation. The reliability of geophysical interpretations can be improved by including direct substrate observations in campaigns. Here, the benefits of performing detailed sediment logging alongside geophysical surveys are exemplified, together with descriptions and explanations of associated method adaptations.Through a combination of method updates and applied studies, this thesis highlights the great potential for geophysical techniques in improving our understanding of glacial processes and outlines potential avenues for further work in this area.
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