Upper Seletar Reservoir was formerly known as the Seletar Reservoir, before the completion of the Lower Seletar Reservoir near Nee Soon, formed by the damming up of the mouth of Seletar River, in 1986. The Seletar Reservoir was built to meet the surge in water demand after World War I. It was completed in 1940 and officially opened on 10 August 1969 by HRH Princess Alexandra. The Singapore Zoo, formerly known as Singapore Zoological Gardens, the Night Safari and the Mandai Orchid Garden are located on the margins of the Upper Seletar Reservoir.