people saw this a destruction of part of the Welsh culture in order to supply England with water. This caused a great deal of controversy, resentment and protest. To try to offset some of the environmental concerns associated with the scheme, some of the stored water was specifically set aside to make special releases to help fisheries, to provide recreational opportunities (canoeing and white-water rafting on the Afon Tryweryn) and to disperse pollution events should they occur. A four megawatt hydro-electric station at the dam was also included in the scheme. Llyn Brenig Further statutory powers were gained in 1973 to construct another major regulating reservoir in the River Brenig valley - Llyn Brenig (). This reservoir was first filled in 1979 providing an additional of storage. This increased the potential for abstraction from the river in the lower reaches to nearly . By 2002 the authorised abstractions had been taken over by three statutory undertakings and British Waterways Board with a total licensed abstraction of . In addition a residual flow of at least 364,000 cubic metres per day is maintained over Chester Weir in all but the most testing of droughts, safeguarding the passage of migratory fish and limiting the ingress of saline water over Chester Weir during high tides. Operating rules The operating rules for the current system are agreed with all the participants and define the circumstances in which flow will be precisely managed. The key measuring location is at Manley Hall (), a gauging station near Chirk. This location was chosen as it was on a section of the river where flow could be readily measured and above the very flat stretch that meanders into Cheshire. The current rules state that when flow exceeds no intervention is required. In practice some adjustment of Bala sluices may take place to increase storage in Llyn Celyn and conversely some releases may be made from Llyn Celyn for recreational or power generation purposes. When the flow at Manley Hall decreases towards 10 m³/s, additional flow is released from Llyn Tegid. If that is insufficient, flow from Llyn Celyn is used to maintain at Manley Hall. In extreme situations where the flow from Llyn Celyn is insufficient to maintain the flow, releases of water from Llyn Brenig are made. Circumstances can arise where even this is insufficient to maintain flows and in such cases drought provisions are agreed which