By the 20th century, Singapore’s population had grown significantly as migrants poured in and settled here. To meet rising water needs, the Water Engineer recommended in 1920 that another reservoir be created by damming Seletar River. This reservoir was thus built in the same year.
Known as Seletar Reservoir then, it was Singapore’s third impounding reservoir, after MacRitchie and Peirce Reservoirs. It was first expanded in 1940 to increase its capacity. Later in 1967, it was enlarged again with the construction of a new dam. When the works were completed two years later, the capacity of the reservoir had increased by four times to more than 22.7 million cubic metres, making it Singapore’s largest reservoir in its time. The reservoir was officially opened by Her Royal Highness Princess Alexandra on 10 August 1969. In 1992, it was renamed Upper Seletar Reservoir to differentiate it from the new Lower Seletar Reservoir.