Grahamstown Dam is the Lower Hunter's major water supply, typically providing 40% of our water. The proportion of water supplied is much higher in times of drought.
Transfers from the Williams River
Grahamstown Dam is classified as an off-river storage facility, storing raw water pumped from the Williams River at Seaham Weir through the Balickera Canal, raised approximately 15m at the Balickera Pumping Station and then flows through the Balickera Canal and Tunnel into the northern end of Grahamstown Dam. On average, 50% of inflow to Grahamstown Dam is pumped from the Williams.
Hunter Water monitors water quality in the Williams River for nutrients before transferring water to Grahamstown Dam. Like most Australian rivers, the Williams is highly influenced by climatic conditions and is consequently highly variable in flow and water quality. Flow and water quality are assessed against pumping rules to minimise the nutrient load transferred to the dam.
The Grahamstown catchment
Grahamstown Dam's small catchment contributes the remaining inflow. The catchment is primarily located on the northern and eastern shores of the dam.
To the north of the catchment Seven Mile Creek fills the dam with runoff from small farms and other minor developments. Approximately 75% of total catchment runoff comes from the northern part of the catchment.
Runoff from the east comes directly from the urban settlement of Medowie through the Campvale Swamps. Water is pumped into the dam via the Campvale Pump Station and finally spills at the Irrawang Spillway.
Hunter Water works closely with landowners and residents in the Grahamstown catchment area to improve the quality of water draining into Grahamstown Dam.