The Jumbles Reservoir is a heavily modified, high alkalinity, shallow reservoir in North West England. It lies in Jumbles Country Park, in the valley of Bradshaw Brook, partly in the Metropolitan Borough of Bolton, Greater Manchester, and partly in Blackburn with Darwen, Lancashire. It was opened on 11 March 1971 by HRH Queen Elizabeth II for the then Bolton Corporation Waterworks (since privatisation the reservoir is now owned by United Utilities).