The river's watershed encompasses the most densely populated areas east of the Jordan River,[1] and it flows through an industrialized area that is home to more than 52% of Jordan's industrial plants, including the Jordan Petroleum Refinery Company. During the summer months, treated domestic and industrial waste-water compose nearly all of the flow, and substantially degrade the water quality. Coupled with over-extraction of water from the underground aquifer and the naturally low base flow of the Zarqa, this has created a major problem, described as one of Jordan's "environmental black spots".[31] and has made rehabilitation of the Zarqa a top priority for the Jordanian Ministry of the Environment.