<p>Assessing the water resources affected by leachate generation in municipal solid waste open dumps is crucial to find suitable solutions for preventing the leachate leakage (especially for landfills located near rivers). This study aimed at evaluating the water quality of the Haraz River located in the vicinity of Amol waste disposal site in north of Iran in terms of different leachate pollutants. For this purpose, four samples of leachate pounds which is formed in different parts of Amol waste disposal site were collected, and the leachate pollution level was determined using the leachate pollution index (LPI). Also, the quality of the river was evaluated using the Iranian Water Quality Index (IRWQI) through water sampling from different parts of the Haraz River. The results showed the water quality status of river is in the medium level before exposure to landfill leachate and changed to relatively poor level immediately after leachate discharge area. However, by taking distance from leachate entry point the quality of the river showed signs of recovery due to self-purification phenomena. The amount of LPI in the Amol waste disposal site (i.e. LPI = 25) compared to the standard amount in the river (calculated based on the standard for wastewater discharge to surface water) (i.e. LPI = 5) shows that the generated leachate with a high level of pollution threatens the surrounding environment particularly the quality of the Haraz River. Finally, novel actions were suggested to prevent the discharge of leachate into the Haraz River. It can be concluded that integrating the surface water quality index and the leachate pollution index can serve as a suitable tool for assessing the impact of landfills on the surface water resources.</p>