What is notable is that the majority of these urban areas are in the upper reaches of either the Trent itself, as is the case with Stoke, or the tributaries. For example, Birmingham lies at the upper end of the Tame, and Leicester is located towards the head of the Soar. Whilst this is not unique for an English river, it does mean that there is an ongoing legacy of issues relating to urban runoff, pollution incidents, and effluent dilution from sewage treatment, industry and coal mining. Historically, these issues resulted in a considerable deterioration in the water quality of both the Trent, and its tributaries, especially the Tame. To bring clean water to the West Midlands, Birmingham Corporation created a large reservoir chain and aqueduct system to bring water from the Elan Valley.