Investigation of Ground Water dynamics in the Lake Victoria Basin using Hydrogeochemical and Isotope Hydrology

Citation:
Kanoti JR. Investigation of Ground Water dynamics in the Lake Victoria Basin using Hydrogeochemical and Isotope Hydrology. Nairobi - Kenya: University of Nairobi; 2013.

Thesis Type:

PhD

Abstract:

Kenya is classified as a water-scarce country with per capita water being below the global benchmark of 1,000 cubic meters. In 2005 the estimated per capita was about 647 cubic meters for all uses. This scarcity is expected to worsen by 2025 when per capita is projected to be about 235 cubic meters. This poses a serious threat to socio-economic development, the integrity of national ecosystems and the quest to achieve the Vision 2030. There is therefore urgency to investigate and understand the available freshwater resources and water dynamics so as to formulate informed policy. This study targets the Nyanzian trough in the neighborhood of the freshwater Lake Victoria. This region faces a lot of water challenges related to water quantity, water quality deterioration, transboundary water issues and perennial flooding.

To counter the challenges, we need to improve our understanding of the water cycle since it is one of the key elements of scientific information necessary for developing policies toward a sustainable management of freshwater resources. Water supplies in the area come from various sources including surface water, shallow and deep wells.

The aim of this study is to investigate the groundwater characteristics using suitable environmental isotope techniques in order to establish the links between groundwater and the surface water for better exploitation strategy. It will investigate and demonstrate if there is any link between the lake water and the boreholes and if water mining is occurring in some regions within the basin.

This study also aims to answer local hydrologic questions about the aquifers through studies with pumping tests and stable isotopes. Specifically, of interest is the amount of dispersion in the deeper aquifer, its degree of hydraulic connectivity, and whether there are signs of younger, shallow groundwater intrusion. On a regional scale, we would like to know what the age and recharge rates of groundwater are at depth, thus allowing the estimates of groundwater flowlines and their changes with shifting deep groundwater usage.

The study will explore the near-surface processes of the land phase of the hydrologic cycle (surface and shallow subsurface processes) in particular the movement of water near the earth's land surface, the physical and the chemical interactions with earth materials accompanying that movement.
Flow system analysis and tracer hydrology will be used to evaluate the water resources within the basin.

This will involve determination of the characteristics of the natural groundwater flow field, flow systems and hydrogeochemical facies analysis of water samples. The definition of the facies and classification of water types in the basin including identification of groundwater origin will be undertaken during this study.

Different methods of analyses and assessment of hydrological flow systems will be used including hydro-chemical and tracer hydrological approaches to delineate flow systems and understanding flow patterns in the Basin. The use of tracer techniques will illustrate the flow pathways, residence times of the water, the hydraulic properties of flow systems, and the mixing of different water compartments if any.

It is envisaged that through this study the general use and acceptance of hydrogeochemical proxies and by extension, isotope methodologies into the mainstream hydrology and water resources management in Kenya will be adopted since isotope techniques may provide, among others, adequate information on recharge conditions, quality and age of groundwater. It may also unravel the role groundwater dynamics contributes to the Lake Victoria waters and to the flooding in the Basin.

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