RP-Department of Water and Environmental Engineering

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Browsing RP-Department of Water and Environmental Engineering by Author "Kilonzo, Fidelis"

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    Assessing the Impacts of Environmental Changes on the Water Resources of the Upper Mara, Lake Victoria Basin: UNESCO-IHE PhD Thesis
    (CRC Press, 2014) Kilonzo, Fidelis
    Growing population and unregulated access to forest land have exerted high pressure on the land and water resources of the recharge areas of the transboundary Mara river, in the Lake Victoria region leading to changes in land and water use patterns in the basin. This thesis considers the interactions among climate change and variability, water quality, land surface cover, hydrology, and human systems, including societal adaptations to changing environmental conditions. The thesis explores the interaction between trends in climatic variables and the feedback response of vegetation variables. The effect of different land cover types on water quality is addressed, and alternative methods to treat data quality for hydrological model inputs and validation are discussed. The Soil and Water Assessment Tool (SWAT) hydrological model was adapted to the tropical watershed experiencing data scarcity, and used to assess the impacts of changes to the climate, land use and management practices. Different scenarios driven by the prevailing natural trends, strategic national development and economic policies were used to asses the potential impacts of changes.
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    Hydrochemistry and source of high fluoride in groundwater of the Nairobi area, Kenya
    (Taylor & Francis, 2008) Marleen, Coetsiers; Kilonzo, Fidelis; Kristine, Walraevens
    This study aims to identify the hydrogeochemical processes influencing the high fluoride concentrations in groundwater of the Nairobi area, Kenya. For this purpose 16 groundwater samples were collected and analysed. Fluoride concentrations above the WHO standard are found in the downstream areas. The high F- concentrations are correlated with high sodium and pH and low Ca2+ concentrations. Weathering of sodium-rich alkaline igneous rocks causes a pH increase resulting in an increase in HCO3- and CO32- by dissolution of CO2. Groundwater becomes oversaturated compared to calcite and calcite precipitation occurs, leading to a decrease in Ca2+. This causes a sub-saturation with respect to fluorite and dissolution of fluorite increases the F- concentration. These reactions were modelled using the PHREEQC model and the results showed a good agreement with the measured groundwater quality, indicating that the proposed reactions are plausible for explaining the observed concentrations in groundwater.
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