Seaham Weir is located near the town of Seaham on the lower reaches of the Williams River. It is owned and operated by Hunter Water. The weir provides a separation between saline tidal water in the Hunter River Estuary and fresh water that flows down the Williams River. The existing components of Seaham Weir consist of a rock weir, two control gates and an orifice style fishway.
The requirement of the study was to develop an integrated fishway for both upstream and downstream migration of fish and flow control gates that could release environmental flows between 10 and 500ML/d.
The study involved:
The design incorporated a fish retention weir primarily to limit fish being expelled from the fishway at low tailwater and also offer the chance for fish within the retention weir to remain near the fishway entrance at low tides.
Another innovative component of the design was to incorporate a submerged and removable weir within the stop board guides downstream of one of the gates to control turbulence within the fish retention weir pool.