Browsing by Author "Kitheka, Johnson U."
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Publication An Assessment of the Spatial and Temporal variations of Groundwater quality in Yatta Plateau in Kitui County, Kenya(IISTE, 2017) Mwamati, Fredrick T.; Kitheka, Johnson U.; Njuru, Peter G.The study is primarily focused on the assessment of groundwater quality in the Yatta Plateau of Kitui County. The study focused on the spatial temporal distribution of key chemical parameters namely pH, TDS, Colour, Total hardness, Turbidity, Conductivity, Total alkalinity, Fluoride and Iron. Groundwater samples were collected four times from the six target boreholes found on the plateau in the period between March 2015 and March 2016. The sampling programme covered two dry seasons and two wet seasons. Key physicochemical parameters were analysed using standard laboratory methods. The water samples were analyzed at the Water Resources Management Authority (WARMA) Water Quality Testing Laboratory in Nairobi. The results of the study show that there is no direct relationship between rainfall and variations of groundwater quality in the Yatta plateau. The influence of water abstraction on water quality was also limited. The dominant influence on groundwater quality in the Yatta Plateau was found to be the geological characteristics of the area. It was however found that there was spatial-temporal variability in different groundwater quality parameters that were analysed. The study recommends integrated groundwater resources management including continuous water quality monitoring in the Yatta Plateau in Eastern Kenya.Publication Hydrology and Best Practices for Managing Water Resources in Arid and Semi-Arid Lands(IGI Global, 2017-07) Kitheka, Johnson U.; Ondieki, Christopher M.The management of water resources is extremely important for survival. Depending on the climate, certain regions require different strategies to maintain sustainable hydrological systems. Hydrology and Best Practices for Managing Water Resources in Arid and Semi-Arid Lands is a crucial scholarly resource that outlines current trends in water management and offers solutions for the future of this growing field. Highlighting pertinent topics such as hydrological processes modelling, satellite hydrology, water pollution, and climate resources, this publication is ideal for environmental engineers, academicians, graduate students, and researchers that are eager to discover more about the issues and processes currently shaping water management technology.Edited References feature peer-reviewed scholarly chapters that are contributed by a variety of experts from around the world. Offering concise discussions of the latest models and concepts within a specific area, these collaborative publications accommodate the research needs of academicians, professionals, and practitioners, and are suitable supplements for graduate and undergraduate courses.Publication Introducing Efficient Low Cost Smoked Pots for Water Purification for Developing Countries(OMICS Publishing Group, 2013) Chung, Dong H.; Kimatu, Josphert N.; Nyariki, Kelvin O.; Su, Kim J.; Onura, Karren N.; Kitheka, Johnson U.Ceramic materials are easy to make using most African soils. They have been used for a long time mainly forcooking and water storage. However, in other low income economies these clay ceramic filters have been shown tohave the potential of being improved by being embedded with carbonaceous materials for water purification. In thisresearch we have produced efficient physiological and biological gravity operated smoked pots for water purification.We used well calculated volume ratios of black clay, red and sand soils (B:R:S) and soil balls; All these were baked atdifferent smoke infusing kiln temperatures for efficient water purification. We analyzed water purification efficienciesof the pot ceramics and the trickling rates at different conditions. We isolated the best B:R:S to be the 40:40:20. Wefound significant reductions in turbidity (99.95%), salinity (21.42%), microbial populations, total dissolved solutes(TDS) (17.19%), pH (1.39%) and electrical conductivity (EC) (16.92%). These ceramics can be crucial for commonor nomadic communities in sub-Saharan rural areas and in times of disaster to guarantee a cheap continued supplyof clean potable water for better health amongst the low income earning societies.Publication Suspended sediment transport in a tropical river basin exhibiting combinations of land uses/land covers and hydroclimatic conditions: Case study of upper Athi Basin, Kenya(Elsevier, 2022-06) Kitheka, Johnson U.; Kitheka, Lynnete M.; Njogu, Imelda N.Study region The Upper Athi River Basin (Lat: 1°25′17.61°S and Long: 37°15′29.55°E) in Kenya, East Africa. Study focus The effects of land use/land cover type on suspended sediment concentrations and yield were investigated in the upper Athi river basin in Kenya. The suspended sediment concentrations and yield, river discharges, water levels and flow velocities were monitored in stations established at the outlets of sub-basins and also at the outlet of the main basin in period 2012–2015. New hydrological insights The magnitude of river discharge in the upper Athi river basin is not only a function of the magnitude of rainfall, but combination of land uses/land covers determined the magnitude of sediment yield in the sub-basins. The highest sediment yield occurred in a semi-arid sub-basin dominated by savannah grassland and livestock grazing. The lowest occurred in the high rainfall sub-basins dominated by forest with mixed farming and settlements. Significant sediment transport commenced at an effective river discharge of 405 m3s−1 which is a frequent discharge event resulting in significant sediment load transport in most rainy seasons and years. The magnitude of suspended sediment discharge is a function of the magnitude of rainfall such that the greatest sediment transport occurs during the long rainy seasons (54%) as compared to 41% during the short rainy season. The total annual suspended sediment load in the basin ranged 2.11–3.77 × 106 tons.yr−1 and sediment production rate ranged 205–366 tons.km−2.year−1.Publication Tana Delta and Sabaki Estuaries of Kenya: Freshwater and Sediment Input, Upstream Threats and Management Challenges(Springer, 2016-03-23) Kitheka, Johnson U.; Mavuti, Kenneth M.This study is focused on the determination of the extent to which changes in river freshwater and sediment input affects the sustainability of the Tana Delta and Sabaki estuaries in Kenya. The study involved the determination of river freshwater and sediment fluxes, as well as water exchange and sediment fluxes at the mouths of the two estuaries. The horizontal and vertical distributions of tidal current velocities, salinity and total suspended sediment concentrations (TSSC) within the estuaries enabled determination of the degree of stratification and the extent to which mixing of seawater and freshwater leads to the formation of the maximum turbidity zone (TMZ) in the two estuaries. The two estuaries are important for biodiversity conservation, sustainability of socio-economic livelihoods and provision of global environmental benefits. The study shows that the hydrologic dynamics controlling water circulation including the trapping and exchange of terrigenous sediments in the two estuaries is a function of the river discharge and tidal forcing. In the much smaller Sabaki estuary, there has been a reduction in freshwater input and an increase in sediment supply leading to heavy accretion. The shallow nature of the Sabaki estuary ensures reduced penetration of the semi-diurnal tidal wave into the estuary and seawater intrusion is restricted to 2.5 km of the estuary. On the other hand, there has been a substantial reduction in both freshwater input and sediment supply into the Tana Delta. This has led to deepening of the estuary channels with the result that tidal wave penetrates much deeper into the estuary and seawater intrudes up to 10 km inside the estuary. The tidal asymmetry in the two estuaries is characterized by ebb tidal flow dominance due to presence of mangrove forests, wide intertidal areas and freshwater input. This has resulted in net export of sediments out of the two estuaries. However, the cohesive clay sediments are trapped within the estuaries in mangrove forest wetlands and in sheltered intertidal areas that are now occupied by mudflats. The shallow Sabaki estuary experiences greater rates of water and sediment exchange as compared to the relatively deeper Tana estuary. The changes in freshwater and sediment supply into the two estuaries were attributed to landuse change, damming and climatic variability. The major impacts in both estuaries include high turbidity, heavy sedimentation, changes in beach morphology and degradation of the marine ecosystems such as the coral reefs and seagrass beds. In the Tana delta system, the impacts include high turbidity, alteration of the morphology of the delta, degradation of the mangrove forests, coastal erosion and sea water intrusion. The study notes that the proposed large-scale hydropower and irrigation projects in the Athi-Sabaki and Tana river basins have the potential of causing massive degradation of the two estuaries. The paper puts forward recommendations for sustainable management of the two estuaries in Kenya.Publication The effect of river flow and land use land cover dynamics on reservoir sedimentation in a small ASAL tropical basin in Kenya(IJISRT, 2023-05-23) Kasuki, M. M.; Kitheka, Johnson U.; Otieno, HesbonKalundu reservoir is one of the water reservoirs in arid and semi-arid lands in Kenya that has been experiencing periodic siltation since 1950s. Lack of data and information on the hydrological processes and land use practices has limited implementation of localized strategies to minimize sedimentation in the reservoir. The objective of this study was to determine the hydrological influences and land use practices that contributed to sedimentation of Kalundu reservoir in the period between (2000 – 2021). Hydrological datasets were acquired from three sampling stations established at different points along Kalundu River. Landsat imagery were used in the Land use and Land Cover analysis. Hydrological analysis showed that during the short rainy season, the mean river discharge ranged from 0.44- 1.00m3 /day and 0.11-0.50m3 /day during the long rains. Sediment load discharged into the reservoir was more during the short rains (134,028.84m3 )than during the long rains (28,448.87 m3 ) with a Trap Efficiency of 47.73%and 55.91%, respectively. The river discharge showed a significant relationship with TSSC (r=0.69, Pvalue=0.03), turbidity in the river (r=0.68, R2=0.45, pvalue=0.03) and sediment load (r=0.68, R2=0.46, pvalue=0.03). This results implied high sediment load is likely to be observed during high flows. From bathymetric analysis, Kalundu reservoir decreased its storage capacity by 70% from 500,000m3 in 2013 to 149,902m3 in 2021. This implied that 350,098m3 of sediments were deposited within that period at an estimated rate of 65,317 tons/yr or 2,722 tons/km2 /yr. The total surface area of the reservoir decreased by 11% from 48,500m2 in 2013 to 43,200m2 in 2021.In 2021, the mean water depth in the reservoir was 2.1m and the deepest part was 3.5m. The Useful Life Span of the dam was estimated to be about 3 years. LULC analysis showed that croplands and built-up areas increased significantly within a period 20 years (2000-2020). Bareland and abandoned croplands were attributed to soil erosion in the study area leading to sedimentation of Kalundu Dam particularly during short rainy seasons. Poor farming practices, urban land development activities, heavy infrastructural development and clearing of natural vegetation in the sub-basin were strongly attributed to the increased sedimentation of the dam in the period between (2010-2020).Publication The impacts of water abstraction in tropical rivers: a case of South West upper Tana basin, Kenya(IISTE, 2019-05-31) Mwendwa, Philip K.; Kitheka, Johnson U.; Mwangi, Moses; Otieno, HesbonThe study to determine the impacts of water abstraction in South West Upper Tana Basin which is part of thelarger Upper Tana basin was undertaken in four major rivers, Thika, Kimakia, Kiama and Chania. Data for thisstudy was obtained from the Kenya Meteorological department (KMD), Water Resources Management (WRA)and questionnaire surveys. The questionnaires were administered in the period between January 2018 andDecember 2018 to determine the impacts of water abstraction in both dry and wet seasons. Regression andcorrelation analysis was used to determine the nature and strength of relationships between different variables.The results of the study indicate that the main impacts of water abstraction are hydrological, environmental andsocio-economic. The hydrological impacts include reduced water levels, changes in stream morphology,decreased turbidity and reduced siltation. Socio-economic impacts include increased income from cropproduction and conflicts while environmental impacts were mainly changes in riparian vegetation. The studyestablished that the best combination of impacts of water abstraction in the South West Upper Tana Basin werechanges in water turbidity, decline in water levels, improved crop yields, changes in channel morphology andsiltation with a coefficient correlation r of 0.57 and coefficient of determination R2 of 0.52. To mitigate theseimpacts, there is a need for better enforcement of legislations on water abstraction and the monitoring of the riverbasins to curb water over-abstraction. Public awareness campaigns and involvement of stakeholders could alsominimize these impacts.