The Tryweryn is a river in north Wales. It starts from Llyn Tryweryn in the Snowdonia National Park and after 19 km joins the River Dee at Bala. It is one of the main tributaries of the Dee and has been dammed to form Llyn Celyn. Water is stored in winter when flows are high, and released over the summer to maintain the flow in the Dee (water from the Dee is used as the water supply for large areas of north-east Wales and for the Wirral and much of Liverpool).
The Tryweryn is the site of the Welsh Canolfan Tryweryn national whitewater centre, managed by the Welsh Canoe Association. It is an important river for whitewater kayaking and rafting. The centre features a Café and superb facilities to support whitewater sports. The natural whitewater rapids have been modified (by placing boulders along the river bed) to make them safer and to build playspots. The river is usually considered to be Grade III. Usually between 9 and 12 cumecs (m³/s) are released from the Llyn Celyn dam.
The regular releases from Llyn Celyn in summer mean that kayak events and trips can be planned in advance, and commercial rafting can take place (most whitewater rivers in Wales rely on recent rain to have enough water for kayaking or rafting). There are problems with recreational access to many of the other rivers in Wales, and so rafting and kayaking is not always possible.
Slightly down river from the centre is the Tyn Cornel campsite.