Use of water quality index to assess the impact of flooding on water quality of River Kaduna, Nigeria

Abstract

Flooding is increasingly becoming a yearly occurrence in Nigeria and many parts of the world and is linked to climate change. It comes with a wide range of consequences including the destruction of life and property and surface water pollution. This study used water quality index (WQI) to assess the impact of 2019 and 2020 flood events on the water quality of River Kaduna. Nine water quality parameters were selected based on Nigeria standards, while the weighted arithmetic method was applied in calculating the WQI. The result shows that electrical conductivity, TDS, Cl-, Na, sulphate, and nitrate were all below the maximum standard limits throughout the study period, while Fe and turbidity were above the limits. While other parameters showed varied responses before and after the two flood events, Fe and turbidity were consistently higher after the flood events. The water quality of the river is generally in the extremely poor class, both before and after the 2019 and 2020 floods (WQI > 100). There was a pronounced decrease in water quality at all the sampling stations after both the 2019 and 2020 flood events. The decreasing water quality should be of a public health concern as a large number of people depends on this river for domestic use.