The current study dealt with the impact of the wastes of the Danfali Valley, located on the left side of the Tigris River, on the quality of the water of this river, which is considered the only surface resource for the residents of the city of Mosul, and evaluated the quality of this valley's water for drinking purposes using the Canadian Water Quality Guide. Monthly samples were collected from the water of this valley and were conducted on it. Many physical and chemical tests, in addition to performing a total bacterial count and diagnosing the bacterial species present, were conducted.  The results of this study showed noticeable differences in the values and concentrations of the measured variables between the two sites. At the first site, the highest values recorded were: pH 9.4, turbidity 33.84 NTU, electrical conductivity (EC) 1093μS/ cm, total dissolved salts 587mg/ L, and total hardness 300mg/ L as CaCO₃. At the second site, the corresponding values were slightly different: pH 8.9, turbidity 39.22 NTU, EC 1103μS/ cm, total dissolved salts 480mg/ L, and total hardness 258mg/ L. While the concentrations of orthophosphate and nitrate also reached 0.58 and 0.63mg/ l in the water of the first site, while in the second site their concentrations reached 0.66 and 0.78, respectively. While the results of the Canadian Water Quality Guide showed that the water of the first site was of a questionable type in terms of its use for drinking compared to the water of the second site, since it was of a poor quality and both were unfit for drinking.