1054 Ethiopian Journal of Environmental Studies & Management 10(8): 1054 – 1070, 2017. ISSN:1998-0507 doi: https://ejesm.org/doi/v10i8.7 Submitted: July 10, 2017 Accepted: October 20, 2017 WATER QUALITY ANALYSIS AND EVALUATION USING GRAPHICAL METHODS: A CASE OF LAKE BESEKA, ETHIOPIA HAILE A. SHISHAYE School of Water Resource and Environmental Engineering, Haramaya University, Ethiopia Email: haile.4.hiwot@gmail.com Abstract Water quality analysis and evaluation processes are very important to understand the quality status and trend of water resources. Moreover, a documented water quality data can serve as an input in identifying the geochemical composition and origin of water resources. The aim of this paper was thus to analyze and evaluate the water quality in Lake Beseka and to suggest appropriate lake water management strategies according to the need. To do so, both the standard laboratory experimentation and graphical methods (software like GW Chart and PHREEQC) were used. Accordingly, the origin of the lake water was found to be deep groundwater with a dominant geochemical composition of sodium bicarbonate. Moreover, the temporal variations and correlations of the water quality parameters were also analyzed. The levels of most of the measured water quality parameters in the lake were found to decrease with time. Finally, the suitability of the lake water for irrigation and drinking purposes was analyzed using the standard methods and compared with the global standards. Lake Beseka was thus classified as unsuitable for both purposes. Key Words: Water Quality Evaluation; Lake Beseka; Origin and Geochemical Composition; Trend Analysis Introduction Water quality evaluation helps to understand the extents of contaminants in water and the overall hydro-geochemical nature of water (Harley, 2002). Contaminants in water may cause different negative impacts such as diseases. Therefore, knowledge of the chemical composition of water may help to design appropriate water resources management strategies. Any parameter in water has its own concentration limit if it is in use for any purpose. In this regard, the maximum contaminant limits (MCL) of ionic concentrations and values of the physical properties of water designed by different organizations are the guides to use water for any purpose (SON Governing Council, 2007; USEPA, 2012 and 2012; WHO, 2006). The widely used water quality standard in Ethiopia is that of the WHO standard. Thus, any value beyond the MCL may cause problems. High levels of nitrate and nitrite, caused mainly by fertilizers, for example, can lead to This work is licensed to the publisher under the Creative Commons Attributions License 4.0