Lake King William is a large hydroelectric impoundment nestled in the heart of Tasmania's Central Highlands, created in 1950 when Hydro Tasmania constructed the 70-metre Clark Dam across the Derwent River. In the late 1960s, an additional 6 metres was added to the dam wall, significantly increasing the lake's storage capacity. As a working hydroelectric reservoir, the lake experiences large fluctuations in water level throughout the year due to ongoing electricity generation demands. The water is notably clear, allowing anglers to polaroid fish along steeper shorelines — a hallmark of quality Tasmanian highland fishing. The lake is managed as a wild trout fishery by the Inland Fisheries Service, and its many inflowing creeks and rivers provide extensive natural spawning habitat, supporting a self-sustaining fish population of exceptional quality.