Seaham Weir, which is located on the lower Williams River near Seaham, is used to separate the downstream tidal estuarine salt water from the upstream fresh water. The weir structure includes a fishway for fish migration, and gates that are used to control the upstream water level. The canal intake is located immediately upstream of Seaham Weir at Boag’s Hill and includes a radial gate, trash rack and a water quality monitoring station.
Balickera pump station and canal are used to transfer water from the Williams River to Grahamstown Dam. This conveyance system includes around 5 kilometres of canal and a pump station part way along that lifts the water around 15 metres. The decision of when to pump water is based on availability of water in the river, space in the dam, and the quality of the water in the river. Pumping is suspended if nutrient or algae cell levels at Boag’s Hill intake exceed pre-determined limits. While the average flow in the Williams River is around 1,000 megalitres per day, the distribution of this flow is highly variable, with flows being below 100 megalitres per day around 50 per cent of the time but also having capacity to be more than 100,000 megalitres per day. The operation of the pump station is therefore opportunistic by necessity, with pumping only possible following rainfall in the catchment when there is sufficient flow and appropriate quality in the Williams River.
Balickera pump station has six large pumps with a combined capacity of 1,350 megalitres per day - a small proportion of possible flows in the river, which can exceed 100,000 megalitres per day in a major flood. The Balickera pumping concept is therefore designed to transfer flows from the very high flow periods that would otherwise just make their way out to sea.
Hunter Water is currently investigating the opportunity to increase the capacity of Balickera pump station to make greater gains from these very high flows. Water stored in Grahamstown Dam is accessed for supply to customers at George Schroder pump station. This pump station delivers water through twin parallel mains to the Grahamstown water treatment plant at Tomago. All water from Grahamstown Dam is fully treated before distribution to customers.