ABSTRACT
The water in River Kaduna is used for; domestic purposes, fishing, recreational activities as well as irrigation of crops.However, literatures have revealed that there are lots of anthropogenic activities occurring within the middle stretch of the river that could likely deteriorate its water quality as it flows through the Kaduna city metropolis. Hence, this research was targeted at evaluating the water quality of the middle stretch of River Kaduna with respect to seasonality and land use, mapping the water quality of the catchment using Geographic Information System (GIS), determining Water Quality Index (WQI) for the sampling sites considered and finally, optimizing the number of sampling sitesand water quality parameters analyzed. These were achieved by using standard methods to analyze 13 water quality parameters from samples collected at 15 sampling sites along the middle stretch of River Kaduna on a monthly basis for a period of 12 calendar months. The water quality parameters analyzed includes temperature, turbidity, total dissolved solids (TDS), chloride ion (Cl-), pH and electrical conductivity (EC). Others are; dissolved oxygen (DO), 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), iron (Fe) and manganese (Mn). Laboratory results were subjected to different software packages (ArcGIS 10.5,JMP 13, CorelDRAW X7 and VB.Net 2017) and it was shown that the water quality of River Kaduna was more deteriorated during the dry season. However, COD and TP were found to be the only parameters that never met the requirement set by FEPA throughout the sampling period irrespective of the sampling location and season. This is because the least measured concentrations of COD and TP were 35.34�0.1 mg/l and 0.109�0.05mg/l, respectively as against their respective permissible limits (20 mg/l and0.1 mg/l).Built-up, industrial, and agricultural land uses contributed significantly to the impairment of River Kaduna water quality while vegetation (forest coverage) mitigated the deterioration of the vii water quality to a certain degree. GIS mapping was able to identify the water quality of the non-sampling points within the monitored portion of the river. In addition, the WQI (Canadian) revealed that the water quality of 11 sampling locations were marginal as their index values ranged from 48.51 to 63.62 however, the remaining 4 sampling locations had poor index values ranging from 23.41 to 30.85. These sampling sites with poor WQI values were located at the confluence points of; Kutimbi stream (between Narayi and Barnawa towns), Omo stream (at Kigo road new extension), Nigeria Breweries drainage (at Kakuri) and River Rigasa. An equation for predicting the WQI along River Kaduna was developed as; ?????=0.0194??2+0.0006??+48.9697 where: ????? and ?? represent predicted Canadian WQI and distance away from Kakuri along direction of flow respectively.Furthermore, the 15 sampling sites monitored fell into two major clusters viz: moderately polluted sites and highly polluted sites which correspond to sampling sites having marginal and poor WQI respectively.Analyzed laboratory results further revealed that 8 of the 13 water quality parameters examined (turbidity, TDS, Cl-, EC, DO, COD,TN and TP) were critical parameters on a factor loading>0.75 and accounted for 75.78% of the variation in water quality of the river.Regulatory agencies were advised to check the anthropogenic activities occurring at the hot spot areas shown in the GIS maps especially at Kakuri, Tudun Wada and Rigasa communities so as to put in place appropriate mitigation measures