Browsing by Author "Largier, John"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Open Access
    Circulation through the mouth of Langebaan Lagoon and implications
    (1999) Krug, Marjolaine; Largier, John
    In March 1997 a two-weeks field survey was conducted in Langebaan Lagoon and Saldanha Bay. The aim of this survey was to farther our understanding of the processes driving the mixing and the exchange at the Langebaan Lagoon-Saldanha Bay interface. The parameters measured included currents, water-levels, temperature, salinity, density and wind. The nature of the flow at the Langebaan Lagoon inlets was ascertained by combining statistical analysis of the measurements to a theoretical understanding of the system hydrodynamics. The flow in the vicinity of the straight was predominantly driven by the tide. It was found that during high tidal range periods, there existed an asymmetry between the ebb and the flood flows at both of the lagoon's inlets. When tidal forcing was strong, water particles released at the lagoon inlets during the ebb were subject to long drifts. The outflow from the east inlet appeared to take the form of a turbulent jet. At the west inlet strong frictional interactions between the flow and land boundaries occurred, causing the flow to rapidly expand and lose momentum and therefore impeding the formation of a jet. It was established that, generally, buoyancy forcing on the Langebaan Lagoon outflow would be small and that water issuing from the lagoon during the ebb would remained attached to the sea-bed as it propagated into Saldanha Bay. However, when Saldanha Bay was strongly stratified, the east inlet ebb jet would lift off from the bottom as it reached the 8m depth contour. The large drifts resulting from the sink-like nature of the inflow and the jet-like nature of the outflow induced a very rapid and strong exchange between Langebaan Lagoon and Saldanha Bay. The propagation of the lagoon effluent also contributed extensively to vertically stir the water-column in Big Bay. As the tidal range weakened, the regions of influence of the ebb and the flood overlapped to a greater extent and the exchange between the lagoon and the bay decreased significantly. The asymmetry between the ebb and the flood flows at the Langebaan Lagoon inlets generated a Lagrangian residual circulation, with the east inlet constituting the entrance for Saldanha Bay water, while the west inlet would be the exit route for Langebaan Lagoon water. Southerly winds, contributed to the overall residual circulation by driving water out of the Lagoon. Bibliography: 126-133 pages.
  • Thumbnail Image
    Item
    Open Access
    An environmental overview of the Walvis Bay 'Bay Area', Namibia
    (1996) Heather-Clark, Stuart Andrew; Largier, John
    This dissertation forms part of a process which began when DANCED initiated the first stages of a project aimed at aiding the Namibian Government in the development of an Integrated Coastal Zone Management _Plan for the coastline of the Erongo Region. DANCED requested the assistance of the MPhil students, from the Department of Environmental and Geographical Science of the University of Cape Town, in the compilation of a baseline report for the region. The first step involved the collection and synthesis of baseline data on all environmental factors (natural and social) pertaining to the Erongo Region. This was followed by individual research dissertations by each member of the class. After review of the Baseline Report, the greater Walvis Bay 'bay area ' was identified as a priority area in terms of coastal zone management of the Erongo Region. The aim of this dissertation is thus to provide an environmental overview of the Walvis Bay ' bay area' that can assist planners and relevant authorities in the effective management the area. Firstly, the importance of the study area as a conservation area is established. It is noted that the Walvis Bay wetland is one of the top five most important wetland areas in Africa. Secondly, there is little co-ordination and communication between the authorities that have jurisdiction over portions of the study area and this has led to ineffective management of the area. Thirdly, the study area is defined and the major human activities operating within the study area are identified and described.
  • Thumbnail Image
    Item
    Open Access
    Sand-storage dams : an alternate method of rural water supply in Namibia
    (1997) Hartley, Peter Alexander; Largier, John
    The costs of establishing and installing a borehole are high, ranging from R 57 000 to R 180 000 depending on the depth of hole drilled and type of pump installed (DR WS, 1996). Because of these high costs, the Namibian Government has historically taken responsibility for the provision, operation and maintenance of rural water supply. However, in accordance with the principles advocated in the country's new Water and Sanitation Policy (WASP), an emphasis has been placed on shifting this responsibility to the communities utilising these water supplies (DWA, 1993). In April 1997, the Directorate of Rural Water Supply (DRWS) implemented a programme for the "Community Management of Rural Water Supply". This programme is to be phased in over nine years and during this time rural communities are expected to gradually take over full responsibility for the operation and maintenance costs of their water supply. In the final stage of this programme it is envisioned that these communities will be required to replace broken equipment, and provide new installations themselves (DR WS, 1996). Expecting rural communities to pay for the full cost recovery of their water supply will result in obvious socio-economic impacts on these communities (Sekhesa, 1997). However, the present reliance of many rural communities on groundwater resources gives them little alternative but to accept responsibility for the high costs associated with boreholes. This dissertation therefore, aims at assessing the feasibility of developing sand-storage dams as an alternate supply of water in the rural areas of Namibia.
  • Thumbnail Image
    Item
    Open Access
    Water circulation within Tomales Bay, California, U.S.A. : a Mediterranean climate estuary
    (2003) Harcourt-Baldwin, Jenny-Lisa; Largier, John; Brundrit, Geoff
    Tomales Bay, California, situated along the west coast of the United States of America, in the mid-latitudes at 38° 13' 50" N, 122° 58' 30" W, was chosen as the study site for the "Biogeochemical Reactions In Estuaries" (BRIE) project of the "land Margins Ecosystems Research" (LMER) program of the National Science Foundation in the U.S.A. Research on terrigenous inputs, air-sea exchange, sediment-water exchange, ocena-bay exchange and internal cycling in estuaries was conducted. This thesis addresses the ocean-bay exchange section in identifying and describing the estuarine water circulation and its variability, both temporally and spatially, that drives the observed water column structure in Tomales Bay and the effect of wind driven coastal upwelling on the estuary.