Water is a vital resource. In the human body, for example, water takes up more than half of the body weight. Studies have shown that a person will die if he/she is devoid of water for three days. Water is also consumed for numerous domestic and economic activities including cooking, washing, irrigation, and dyeing.

Seawater contains salt and other constituents and thus is not suitable for drinking, irrigation or operating machinery. We depend on freshwater.

 

 

 

Water changes states in the natural environment. Liquid water on the surface evaporates and becomes clouds in the air; when a certain mass is reached the water turns into rain or snow and falls upon the ground. This is the Water Cycle. Natural freshwater comes only from rivers, lakes and groundwater.

 
 

 

Only about 2.5% of all water on earth is freshwater (about 35 million cubic kilometres), most of which is in the form of ice (accounting for 68.7% of all freshwater), groundwater (accounting for 30.1%), and the remainder in lakes, marshes, rivers and other freshwater resources(accounting for 1.2%). Of all freshwater, only 30.5% (about 10.68 million cubic kilometres) is available for human uses.

Globally, the average water volume available to each person is 1,530,000 cubic metres, but 98.7% of this is groundwater that is not easily accessible. Around the world,nearly 700 million people lack access to clean water.
 
 
There are 17 reservoirs in Hong Kong, with an overall capacity of 586 million cubic metres. The amount of water collected in the reservoirs varies each year, and hence the government has been purchasing a certain volume of Dongjiang water from the Guangdong Provincial government each year since 1960. From 1998 to 2015, the average volume of Dongjiang water supplied to Hong Kong was about 700 million cubic metres each year. In addition to the water storage in reservoirs, Hong Kong is one of the few places that have abundant water supplies.

However, as the population increases, water consumption is also in a rising trend. Hong Kong's annual water consumption is 950 million cubic metres. In the past two decades, overall water consumption rose 50 million cubic metres. If the trend continues, or rainfall is drastically reduced, we may face water shortages in future.
 
Water supplies in Hong Kong:
The first reservoir in Hong Kong – Pok Fu Lam Reservoir — was constructed in 1860 and began supplying water in 1863.
Plover Cove Reservoir is the Hong Kong's first reservoir built from a coastal inlet.
The last built reservoir in Hong Kong – High Island Reservoir — was completed in 1978, It ranks first in water capacity among all reservoirs in Hong Kong.
Sha Tin Water Treatment Works was completed in 1964, and today treats the most drinking water among all 21 water treatment facilities in Hong Kong.
 
Water consumption in Hong Kong

According to Government data, average daily domestic water use per capita from 2009 to 2015 was 18% more than global average. In 2015, average annual water consumption per capita in Hong Kong was 133 cubic metres: about the volume of a double-decker bus.

Domestic use accounts for the largest proportion of overall water consumption, about 54%; next are commercial activities, accounting for about 25%; the third is flushing, about 8%; the remainder is used for industrial, construction and others.