City Mill River is part of the Bow Back Rivers in London, England. It formerly fed City Mill, used for the production of chemicals in the late nineteenth and early twentieth centuries. In the 1930s, the mill was removed and the river was isolated from the tides by the construction of locks at both ends. City Mill Lock, at the southern end, has been refurbished and reopened in 2010. History City Mill River leaves the old channel of the River Lea at its northern end, and flows in a south-easterly direction, originally to City Mill. Town plans from 1895 and 1923 both indicate that it was used for the production of chemicals. The mill straddled the channel, and a bypass stream flowed to the west of the present course, to meet the Waterworks River below the mill. The discharge from the mill was into a large pool, which also formed a part of the Waterworks River. By the late 1920s, most of the Bow Back Rivers including the City Mill River were in serious decay, and the Lee Conservancy Board, jointly with West Ham Corporation, obtained a government grant as part of an unemployment relief scheme to carry out a number of improvements to the rivers. The work was authorised by the River Lee (Flood Relief) Act of 1930, and work began in 1931, taking four years to complete. The course of the river was largely unchanged by the improvements, except at the southern end, where the mill was demolished, and the channel was routed through the mill site. Part of the mill basin was filled in, and the river joined Bow Back River, which was moved slightly further to the north, away from Bow Road and Stratford High Street. The Waterworks River, to the east of the mill basin, was widened and routed further to the west, and a connecting lock was built between the new course of the City Mill River and the new course of the Waterworks River. The river ceased to be tidal, as City Mills Lock isolated the southern end from the tidal Waterworks River, and Carpenter's Lock isolated the northern end, allowing the river to be maintained at the same level as Limehouse Cut. It became semi-tidal, since the water level in Limehouse Cut was maintained by Bow Locks, but high tides overtopped the gates, resulting in there being fluctuations at spring tides. City