Water quality index for assessment and mapping of groundwater quality in Webuye municipality, Kenya

Abstract

Promotion of access to water as a human right has gained a lot of emphasis from various stakeholders in the recent past. This is well articulated in UN human Rights works, the goal number 6 of Sustainable Development Goals and the Secretary-General’s Call to Action for Human Rights. While trying to enforce this, it is important to consider the challenging dynamics in which water quality affects the realization of this goal. Determination of water quality therefore is a key measure to ensure that while promoting access to water its suitability for usage is enhanced. The objective for this study was to carry out an assessment and mapping of water quality index for groundwater in Webuye municipality. The water quality index for hand dug wells and springs in Webuye was evaluated using Weighted Arithmetic Water Quality Index Method. Mapping of water quality index was performed in ArcGIS 10.3 carrying out interpolation of Water quality indices of all groundwater samples using Inverse distance weighting (IDW) method. The water quality index was performed on chemical parameters of 53 groundwater sources sampled randomly from 46 hand dug wells and 7 springs. The water quality physiochemical parameters were; Turbidity, PH, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Electrical Conductivity (EC), Salinity, Sulphates, Phosphate and Nitrates. The results show that 69% of water samples from the study area majorly fell in class >100 (Unfit for consumption), class 76-100 (Very poor) were 16%, class 51-75 (poor) were 11%, WQI class 26-50 (Good) 2% and WQI class 0-25 (Excellent). It is recommended that groundwater sources from the area should not be utilized for drinking unless if subjected to full water treatment. Water quality index gives important information for economic planning since per capita water demand is recently increasing while availability of freshwater continues to decline.