Publication: The Effect of Groundwater Recharge and Abstraction on Groundwater Quality in Nairobi Aquifer System
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2022
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International Journal of Engineering Trends and Technology
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Abstract
Using standard procedures, the study analysed water samples from 100 boreholes from Nairobi Aquifer System (NAS) for selected water quality parameters. Data from eleven monitoring boreholes from 2013-2019 was obtained from Water Resources Authority (WRA). The parameters were weighted, and their concentrations were used to develop Water Quality Indices (WQI). Abstraction data was obtained from WRA while recharge was estimated using SWAT Model. A Multiple regression model for WQI, abstraction and recharge variables was developed, and maps were created. Results showed the highest WQI of 0.4001 when recharge was 666,980.16 m3/year and abstraction 54,963,200 m3/year, and lowest WQI of 0.2861 when recharge stood at 346,483.20 m3/year and abstraction 41,586,600 m3/year. A strong correlation between abstraction, recharge, and WQI of R2 0.86was observed. Areas with high recharge and low abstraction exhibited a low WQI of 0.2, while areas with high abstraction rates and low recharge showed relatively high WQI of 0.6. Therefore, it was concluded that water quality improved with decreased abstraction and recharge and deteriorated with increased abstraction and reduced recharge. It was recommended that abstraction be regulated in line with recharge rates and recharge be improved to maintain high water quality suitable for human consumption.
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Jomo Kenyatta University of Agriculture and Technology