Oberon Dam, built in two stages between 1943 and 1959 across the waterway now known as the Fish River, is 232 metres long and 35 metres high.The surface area of the water it holds when full is 410 hectares.It was originally built to supply water to the Glen Davis shale oil refinery and industries around Lithgow as well as the supporting population.It now feeds water into areas served by the Sydney Catchment Authority, largely through a pipeline which conveys water to the base of the geological formation known as First Narrowneck, a short distance south of Katoomba township.