Evaluation of the groundwater quality status using water quality indices in and around Hawassa City, Southern Ethiopia

Abstract

AbstractThis study looked into the quality of groundwater in Hawassa City and its periphery as a baseline survey for the ‘Assessment of Feasibility of Managed Aquifer Recharge’. Water quality was assessed using four water quality indices. Weighted arithmetic Water Quality Index (WA-WQI), Synthetic Pollution Index (SPI), and Entropy Weighted Water Quality Index (EWQI) were used for domestic water quality assessment. Whereas, Overall Irrigation Water Quality Index (IWQ), was used for irrigation water quality assessment. Accordingly, WA-WQI results showed that 6.25 and 93.75% of the water samples were very poor and poor quality status, respectively, making them unsafe for consumption. However, according to SPI, every water sample was unsuitable for usage as potable water. According to the EWQI model, the water quality status of 22.92, 58.33, and 18.75% of the water samples was average, poor, and extremely poor, respectively. Of the three models used for assessing water quality, SPI is the robust. The primary parameters in both models used to estimate the water quality statuses (68–89%) were F–, K+, BOD5, COD, and HCO3–. The Overall IWQ score indicated fair and moderate water quality levels (6.25 and 93.75%), respectively. Sodicity and toxicity hazard classes shared (47–80%) in determining the irrigation water quality status. This result indicates that the aquifer of the city is being contaminated. This requires enforcing strict standards in septic tank construction. Additionally, increasing groundwater recharge from precipitation sources during the rainy seasons to further dilute the concentration and increase aquifer volume is required.

Keywords

• Water quality index
• synthetic pollution index
• irrigation water quality index
• sodicity
• toxicity
• Sanjay Kumar Shukla