Browsing by Author "Nguli, Michael Mutua"

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    Water exchange and circulation in selected Kenyan creeks
    (University of Dar es Salaam, 2006) Nguli, Michael Mutua
    Tides, currents,salinities, temperatures, climatology and surface heat fluxes were investigated from 1995-1998 in Gazi Bay, Tudor and Kilifi Creeks on the Kenya coast in order to improve knowledge on water circulation and exchange between creeks and the ocean. Tidal data was analysed using harmonic analysis and water exchange determined from heat fluxes and temperature gradient. Spring tidal ranges were found to be 3.01, 3.16 and 3.3m, respectively and, distinct response of semidiurnal, diurnal and fortnightly periods especially in temperature, showed strongly restricted flows. Tidal asymmetries, large shallow water and fortnightly tidal constituents occur in the upper shallow reaches of both Gazi Bay and Tudor Creek. Gazi Bay depicts flood dominance whereas Tudor Creek ebb dominance. Tudor Creek in addition is characterized by a baroclinic wave drag. Residence time in Tudor Creek is from 3 days at spring to 7 days at neap, in Kilifi Creek from 2.5-6 days and in Gazi Bay from 1-2.5 days. Seasonal variability of temperatures and salinities reveal two outstanding seasons, NEM and IMLR, with rapid changes in between. February (late NEM) depicts excess evaporation and hypersaline conditions, May (IMLR) strong rains and estuarine conditions. In the ocean, February is characterized by a low oceanic sea level. A rapid increase in the sea level and decrease in the salinity occur at the onset of the IMLR. The results permit the conclusion that residence times determined from temperature data and heat budget provide good estimates for water exchange; however, further improvement can be made by exploring new databases, and upgrading the equipment for radiation measurements at the coastal meteorological stations.