Use of geographic information system and water quality index to assess suitability of groundwater quality for drinking purposes in Hewane areas, Tigray, Northern Ethiopia

Abstract

The study area Hewane is situated in the southern zone of Tigray Regional State, Hintalo Wajirat wereda. It is geographically located between 1444000 to 1454000m N and 550000 to 558000m E with an aerial extent of 47.66 sq. km. The study was conducted having an objective of assessing suitability of groundwater quality for drinking purposes through geographic information system (GIS) and water quality index (WQI). Ten groundwater samples were collected from the study area and 13 physicochemical parameters such as TDS, TH, Alkalinity, pH, EC, Temperature, Na⁺, K⁺, Mg²⁺,Ca²⁺, Cl^-, HCO₃^- and SO₄^2- were analyzed. Inverse distance weighted (IDW) interpolation method has been used to generate the spatial distribution of the groundwater physico-chemical parameters and water quality index map. To estimate the water quality index, 9 parameters have been considered: pH, Na⁺, K⁺, Mg²⁺,Ca²⁺, Cl^-, HCO₃^-, SO₄^2-, and TDS. The WQI estimated for the groundwater samples of the study area ranges from 86.1 to 180.5 at groundwater samples GWS_2 and GWS_5, respectively. Based on the analysis, most of the area under study falls 70% in poor water class and 30% in good water class. Hence, the result revealed that 70% of the groundwater samples of the study area are hardly suitable for drinking
purposes without water quality management activities.

Key words: spatial distribution, GIS, WQI, groundwater quality, Hewane, Tigray, Ethiopia