High Island Reservoir, Reservoir in Sai Kung District, Hong Kong.

High Island Reservoir is an artificial lake in Sai Kung District, Hong Kong, formed by damming the Kwun Mun Channel between the Sai Kung Peninsula and High Island. It covers about 6.67 square kilometres and holds 281 million cubic metres of freshwater. Two main dams, the East Dam facing the South China Sea and the West Dam facing Port Shelter, plus three smaller saddle dams enclose the basin. The East Dam is armoured with over 2,500 concrete dolosse, each weighing 25 tonnes.

The government began construction in 1969 after riots in 1967 highlighted dependence on water imports. Completion came in 1978 following nearly a decade of work during which five laborers lost their lives.

The engineering achievement connected two uninhabited islands to the mainland through massive dams, creating an enclosed storage basin in the open sea. Walking trails along the dam walls today let visitors examine the unusual construction closely and experience how concrete and water meet at this scale.

Visitors should wear sturdy footwear for the walk along the dams, as paths can be uneven and exposed to sun. Early morning or late afternoon hours offer more comfortable temperatures and softer light for exploring the area.

The reservoir was the first large-scale scheme to enclose a sea channel with dams, and its design by Binnie & Partners included grouting techniques that were advanced for the 1970s. A blue anchor-shaped stone beside the East Dam road commemorates the five workers who died during construction.