Ndarugu River, Kenya, during its course through the different agricultural and industrial areas of\nGatundu, Gachororo and Juja farms, receives untreated industrial, domestic and agricultural waste\nof point source discharges from coffee and tea factories. During wet season the water is also polluted\nby non-point (diffuse) sources created by runoff carrying soil, fertilizer and pesticide residues\nfrom the catchment area. This study involved the calibration of water quality model QUAL2K\nto predict the water quality of this segment of the river. The model was calibrated and validated\nfor flow discharge (Q), temperature (T), flow velocity (V), biochemical oxygen demand (BOD5),\ndissolved oxygen (DO) and nitrate (NO3-N), using data collected and analyzed during field and laboratory\nmeasurements done in July and November-December 2013. The model was then used in\nsimulation and its performance was evaluated using statistical criteria based on correlation coefficient\n(R2) and standard errors (SE) between the observed and simulated data. The model reflected\nthe field data quite well with minor exceptions. In spite of these minor differences between\nthe measured and simulated data set at some points, the calibration and validation results are acceptable\nespecially for developing countries where the financial resources for frequent monitoring\nworks and higher accuracy data analysis are very limited. The water is being polluted by the\nhuman activities in the catchment. There is need for proper control of wastewater by various\ntechniques, and preliminary treatment of waste discharges prior to effluent disposal. Management\nof the watershed is necessary so as to protect the river from the adverse impacts of agricultural\nactivities and save it from further deterioration.
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