The Hawkesbury River has its origin at the confluence of the Nepean River and the Grose River, to the north of Penrith and travels for approximately in a north–easterly and then south–easterly direction to its mouth at Broken Bay, about from the Tasman Sea. The Hawkesbury River is the main tributary of Broken Bay. Secondary tributaries include Brisbane Water and Pittwater, that together with the Hawkesbury River flow into Broken Bay, and thence into the Tasman Sea north of Barrenjoey Head.