During the early development of Hong Kong, as the city grew and the demand for water increased, hillside streams and rivulets could not provide residents a stable water supply. The government thus constructed Pok Fu Lam Reservoir as the first reservoir in Hong Kong.
Due to technological constraints on reservoir building at that time, the location had to take into account water flows downstream. Stored rainwater in reservoir could follow mountain slopes to reach the dense population below. As the Pok Fu Lam Valley is a valley situated well above and yet not too far away from the urban centre, reservoir was proposed to be built in the Pok Fu Lam region.
And during the century, to solve the keen demand for water, expansion projects of the Pok Fu Lam Reservoir were commenced. The government also constructed more reservoirs in various regions of Hong Kong.
However, relying on rainfall from natural catchment as the main source is not very stable, because this depends on the weather and climate...
Source: Water Supplies Department, "Water of a Barren Rock - 150 Years of Water Supply in Hong Kong" by Ho Pui-yin
Image: Wikimedia Commons