The Coquitlam River originates at Disappointment Lake in the Coast Mountains near Indian Arm. It flows south into Coquitlam Lake, a reservoir behind Coquitlam Dam, which provides a large portion of Vancouver's drinking water. The upper portion of the river and Coquitlam lake are part of the Metro Vancouver watershed. Below the dam the Coquitlam River continues to flow south, reaching the Fraser River between the cities of Coquitlam and Port Coquitlam, suburban municipalities located in Metro Vancouver.