Surface and ground water have been under increasing threat of pollution in recent years due to improper management of vast amount of wastes generated by various human activities. Improper dump sites have served many years as ultimate disposal site for all types of waste; municipal solid waste, industrial sewage and hazardous waste in developing countries such as Ethiopia. Physical, chemical and biological processes interact simultaneously to bring about the overall decomposition of the wastes. One of the by-products of this mechanism is chemically laden leachate and it is a potentially hazardous waste from waste disposal sites. If not deal properly such kind of dumping site can cause pollution to groundwater (because of Leachates) and surface water (through contaminant transportation by flooding and ground water movements). Therefore, this study investigates the spatial and temporal variation of ground and surface water quality within the Chilanchil Abay water shed during dry and wet season due to waste disposal site of Bahir Dar city. Water samples were collected from 5sampling points of surface water and 6 sampling points of ground water from 30th march to 20th august by monthly period. Over 15 water quality parameters such as pH, TDS, Electrical conductivity, Turbidity, Temperature, DO, TH, BOD, COD, TC, NO3- , PO43-, Cr, Mn and Pb were analyzed for both ground and surface water. It was found that water quality parameter such as TH, BOD, COD, NO3-, Mn and Pb were within the acceptable limit for both ground and surface water while the remains were fluctuated depending on the sample period. The water quality analysis results show that spatial and temporal variation have a significant on the distribution of physico-chemical, microbial, heavy metal and nutrient parameters along the water shed. Moreover, the overall status of surface and ground water quality of the study area was assessed by Canadian Water Quality Index. The analyzed result showed that the Chilanchil Abay water shed water quality status ranges from 15.87 to 36.6 for surface water (poor status) and 42 to 46.2 for ground water (marginal status).