Reservoirs in Hong Kong are spread fairly evenly over the entire 1,104 km2 of Hong Kong. There is plenty of space for small reservoirs in Hong Kong, as the hilly areas provide valleys suitable for water storage. However, the larger reservoirs, i.e. High Island Reservoir and Plover Cove Reservoir, were built differently. Dams were built where the reservoir's edge was proposed to be, sea water was drained out and replaced with fresh water.