Browsing by Author "Murry-Hudson, M."
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Wolski, P.; Masaka, T.; Raditsebe, L.; Murry-Hudson, M. (Botswana Society, NaN, 2005)[more][less]
Abstract: Seasonal changes in inundation area and peak flood occurrence in the Okavango Delta are analysed using a multiple regression technique. The multiple regression models developed constitute useful and simple tools for predicting inundation area and peak flood occurrence in the Okavango Delta. The regression model for monthly inundation area achieves a coefficient of determination of 0.80 and standard error of 538 km². Explanatory variables in the model are various expressions of long-term and short-term antecedent rainfall and inflow conditions. The model for flood peak occurrence can be used for accurate predictions only in the Jao-Boro distributary, for which it achieves a coefficient of determination of 0.85 and standard error of 15 days, with distance to Delta inlet and an expression of flood size as explanatory variables. Propagation of the flood in the two other analysed distributaries, Maunachira-Khwai and Mboroga-Santantadibe, is complex and its quantitative description appears to be beyond the capacity of a simple regression approach. Additionally, the analyses presented provide insight into the role of storage in the dynamics of flood in the system: hydrological inputs are accommodated in the large system storage, and hydrological response is strongly dependent on the factors affecting (slow!) release from that storage. Based on the analyses, the classic model of kinematic flood wave propagation has been adapted accordingly. URI: http://hdl.handle.net/10311/954 Files in this item: 1
Wolski 2005 Aspects of sea.pdf (2.080Mb) -
Wolski, P.; Murry-Hudson, M.; Fernkvist, P.; Liden, A.; Huntsman-Mapila, P.; Ramberg, L. (Botswana Society, NaN, 2005)[more][less]
Abstract: Groundwater under islands in the Okavango Delta is a known sink of inorganic dissolved minerals, preventing salinisation of this virtually enclosed evaporation-dominated hydrological system. The Okavango Delta is an oligotrophic, yet very productive system, and it is important to understand sources, pathways and recycling of nutrients in order to fully comprehend its ecology. In order to investigate the role of islands as nutrient sinks, concentrations of nitrogen and phosphorus, as well as major inorganic ions were measured in island and floodplain groundwater. The electrical conductivity was found to be up to 50 times higher in the island centre groundwater than in the surrounding floodplain groundwater. The amount of total phosphorus was found to be up to 400 times higher and total nitrogen up to five times higher in the interior of the island than in the surrounding floodplain. These show that major nutrients are, like other inorganic ions, accumulated under islands. Importantly, the ratio of nitrogen to phosphorus was 5:1 in floodplain water and water in island fringe soils, but 1:4 in island centres. his indicates an intensive removal of nitrogen along the floodplain-island groundwater flow path by the floodplain fringe and riparian biota, resulting in a relative enrichment in P. URI: http://hdl.handle.net/10311/950 Files in this item: 1
Wolski 2005 Islands.pdf (1.469Mb)
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