Land Use Effects on Spatial and Seasonal Variations of Water Quality in Thika River Sub-Catchment, Upper Tana Basin, Kenya
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Date
2024-09
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Kenyatta University
Abstract
The study examined effects on physicochemical and microbial water quality of the Thika River in the upstream, midstream, and downstream sections, and between dry and rainy seasons of 2021. The water samples collected were tested for turbidity, pH, total coliform & fecal coliform, nitrates, and Sulphates at Kenya Water Research Institute (KEWI) laboratories. R-studio was used to calculate the mean values and t-test performed at 95% confidence interval to determine the seasonal variation of the physico-chemical parameters in the two seasons. Temperature measurements in the upstream, midstream and downstream were 14.93±0.43°C, 14.97±0.34°C, and 14.27±0.19°C, respectively, all within the permissible range of 12-25°C by KEBS and WHO with no significant variation (p=0.4). pH decreased from 6.82±0.13 in the upstream to 6.16±0.15 in the downstream, indicating weakly acidic conditions, with significant differences observed (p=0.009). Turbidity values were between 1.03–3.43 NTU across the river sections, all within WHO and KEBS limits of 5 NTU. Total Suspended Solids (TSS) showed no significant variation (p=0.018). Stream flow and water levels had significant variations, with stream flow increasing from 0.03±0.01 m³/s upstream to 1.25±0.57 m³/s downstream (p<0.001), and water levels rising from 0.14±0.03 m to 0.25±0.07 m (p<0.001). Nitrate concentrations were highest upstream (11.13 mg/L) and lower downstream (5.54 mg/L and 6.37 mg/L), but no significant differences were found (p=0.5). Sulphate concentrations increased from 215 mg/L upstream to 286 mg/L downstream with significant variation (p=0.4). Total coliform levels ranged from 1,630 to 2,089 TC/100 mL, showing no significant variation (p=0.3), while fecal coliform levels ranged from 99 to 315 TC/100 mL, with no significant changes across sections (p=0.3). Seasonal comparisons revealed significant differences in turbidity (p=0.001), water levels (p<0.001), and microbial parameters, with total coliforms and fecal coliforms increasing during the rainy season (p<0.001). Nitrate concentrations decreased significantly from dry to rainy seasons (p=0.043), while sulphate concentrations and other parameters showed significant seasonal variation (p<0.001). Overall, the study concluded that Thika River is fairly of good quality, but there need to establish safeguarding frameworks to enhance sustainability and safety of the water for community use.
Description
A Thesis Submitted to the Department of Geography in Partial Fulfillment of the Requirement of the Degree of Master of Science Integrated Watershed Management, the School of Pure and Applied Sciences, Kenyatta University, September, 2024
Supervisors:
1.George Lukoye Makokha
2.Bancy Mati