Mining activities in many countries around the world pose serious pressure on surrounding water bodies. This study assesses the environmental impact of Murgul mine, one of the longest operated open-pit copper mines in Turkey. A long-term monitoring study was conducted on the surrounding surface water bodies to assess the degree of deterioration/recovery in water quality. Stream water, sediment and mine discharge samples were collected along the flow direction from the drainages under the influence of the mine. Sampling was also performed on the upgradient drainages from the mine to determine the background conditions. Water samples collected were analyzed for major ion and metal contents. pH, temperature, EC and DO contents of the water samples were measured in situ. Dissolved and total metal contents of the stream water samples and the mine discharges were also analyzed to determine the dominant transport phase of the metals. Negative effects of the past mining activities on Murgul stream are visible on the streamside with the thick flotation deposits. During monitoring study, the most severe effect of the mining activities on Murgul stream was observed following the leakage of tailing dam. The impact of this incident was observed intensely up to the confluence of Murgul stream and Borc, ka Dam reservoir, and this was clearly seen in change of pH, EC, sulfate, metal contents and water facies of Murgul stream along flow direction toward Borc, ka Dam. Al, Fe, Mn, Cu, Zn, Pb and Cd exhibited the highest concentration in the dissolved phase of the stream samples. The impact of discharges from mine on Murgul streambed was enormous, and Murgul stream was classified as heavily polluted water (class IV) according to Turkish inland water quality regulations. Significant increase was also observed in metal contents of the stream sediments taken from the downstream from mine, especially for Cu, S, Zn, As, Ba and Mo. Following the control of leakage, prominent recovery in Murgul stream quality was observed in many parameters and stream water achieved class I-II water quality. Results showed that metal loads transported in the suspended phase of stream were more significant than those in the dissolved phase. Current and past flotation slurry deposits near Borc, ka Dam reservoir may pose long-term risk for aquatic life in Borc, ka Dam as a result of metal leaching and need further investigation.