MST-Department of Geography

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Browsing MST-Department of Geography by Subject "Assessment of Seasonal"

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    Assessment of Seasonal and Spatial Variations in Groundwater Quality of Kamiti-Marengeta Sub-Catchment in Kiambu County, Kenya
    (Kenyatta University, 2022) Adongo, Judith Miriam; Mary Makokha; Joy Obando
    The rise in population within Kamiti-Marengeta Sub-Catchment significantly increased the need for essential services such as residential houses and water supply. However, the service delivery of these critical services, especially water supply in the area, has not progressed with the demand. This has forced many housing investors and institutions to turn to groundwater extraction to meet the population's needs. The main objective of the research was to assess variations in the physical and chemical parameters of groundwater in the Kamiti-Marengeta sub-catchment by assessing the following specific objectives: 1. Physical and chemical characteristics of the boreholes and shallow wells, 2. Spatial variations of selected groundwater quality parameters, 3. Effect of seasonal variations on the select groundwater quality parameters, and 4. Perception and opinions of the residents regarding water quality and demand and supply issues. Forty-seven groundwater samples, 30 from deep wells (boreholes) and 17 from shallow wells, were sampled in May 2016 and September 2017 to represent the wet and dry seasons, respectively. Standard methods were used for onsite and laboratory analysis of the physical and chemical characteristics of the samples. The results obtained from sample analysis were compared to the KEBS and WHO standard values to determine the potability of groundwater. The spatial variation of the physical and chemical parameters in the sub-catchment was determined through a one-way analysis of variance (ANOVA) and mean separation procedure with the Turkey test. The kriging gridding methodology in Surfer 13 Golden Software was used to interpolate the spatial water quality parameters and generate thematic contour maps for the tested parameters. The student's t-test performed at a 95% confidence interval was adopted in determining variation in groundwater quality across the two seasons and SPSS and excel to analyze descriptive statistics and the relationship between multiple variables from the social survey. The concentration of turbidity, Ca2+, K+, Fe2+, and F- in some borehole samples and pH units, Ca2+, Na+, and Fe2+ concentration in some shallow wells did not meet the required standard for drinking water by KEBS and WHO. There was a significant difference in levels of DO between Kiwanja and Kenyatta University (p = 0.13) and Kenyatta University and Kahawa Wendani (p = 0.00), total hardness between Bypass and Membley (p = 0.018), and Bypass and Kahawa Wendani at (p=0.041); and turbidity between Kiwanja and Membley (p = 0.011) and between Membley and Kahawa Sukari (p = 0.024). Contour maps for concentration and units of tested parameters in borehole and shallow well samples showed the variation in the physical and chemical characteristics of the groundwater. A significant difference was registered in the mean concentration of EC, Turbidity, Total Hardness, Ca2+, and Fe2+ in boreholes and mean concentration in all parameters in shallow wells except for Mg2+ during the dry and wet season. The social survey revealed that the boreholes were the primary sources of domestic water within Kamiti-Marengeta sub-catchment. Poor water quality was highlighted as the major problem with the water supply by 44% of the respondent, followed by broken water supply by 39% and cost of water by 10%. 7% of the residents did not cite any problem with the water supply. 50% percentage of the residents perceived the taste of water as the most critical water quality attribute, followed by odour at 36% and appearance at 14%. Fifty-six percent of the respondents considered the water safe for drinking, 39% perceived the water unsafe for drinking, and 5% could not gauge whether water was safe or not. The scientific findings on the assessment of the physical and chemical characteristics of groundwater and the social survey findings indicate that groundwater in some parts of the six regions is chemically unfit for drinking. The findings of this study provide baseline information on the quality of the groundwater systems of the area. It also contributes to knowledge of the seasonal variation of groundwater quality of volcanic aquifers like the Nairobi Aquifer System (NAS), which is vital for water quality monitoring