Lack of relatively adequate groundwater data has been one of the most serious problems related to the groundwater potential assessment. To solve these and other related problems needed further detailed water resources investigations (hydro geological and hydro chemical investigations) to indicate some possible ways and mechanisms for sustainable potable water. The main objective of the research is to assess groundwater quality survey and hydrochemistry and hydrogeological and aquifer characterization based on their storativity, transmissivity, depth, and other variables. To achieve these goals, the combined methodology included field work using compass and camera, office work using software’s such as; aquachem-4, GIS and aquitests and lab analysis of water samples were carried out. Data of Nineteen water points in the study area were collected and analyzed. The main lithological units of the study area from the base to the top are the Precambrian basement, the Mesozoic sediments, the Tertiary volcanic rocks and the Quaternary alluvial deposits. The major aquifers of study area are located in the Quaternary alluvial deposits. The transmissivity in the study area ranges from 46.5 to 2180 m2 /day. The hydraulic conductivity in the study area ranges between 1.77𝑥101 and 3.3𝑥106 m/day. The study results showed that the main source of recharge to the Fafen River basin aquifers is the seasonal from the groundwater during the rainy season. Based on geochemical evolution of the groundwater for different sources there are three major water types; Ca-SO4, Na-SO4, Ca-HCO3, were recognized based on the Schoeller plot. Mechanisms and processes of water-rock interaction that are assumed to modify the original chemical composition of groundwater in the studied system are mainly (1) carbonate dissolution, which affects Ca2+ and HCO3-, (2) reverse ion-exchange reactions with clay minerals that affect Na+ and Ca2+ (3) dissolution of silicate minerals that affect Na+. The suitability of groundwater in the area for domestic use: very hard to hard and fall above the standard limits of WHO (2011) and Ethiopian standard (2013). Sodium, Chloride, Sulphate, Nitrate and Fluorite are within the WHO and Ethiopian Standards permissible limits), but few parameters are falls above the WHO (2011). The suitability of groundwater in the area for irrigation as follows: SAR is low, Sodium percent is generally from good to excellent, Residual Sodium Carbonate is suitable, Magnesium hazard is suitable, so the water quality in the study area indicates that it is suitable for irrigation purpose. Key Words: Upper Fafen catchment, assessing groundwater quality, potential assessment, aquifer characteristics.