Water is a natural resource, and no carbon dioxide is produced when it is used in natural conditions. However, as cities and technologies develop, huge amounts of energy are used for treating drinking water and wastewater, generating massive volumes of carbon dioxide.

Carbon dioxide is a greenhouse gas and is a "culprit" in global warming. Global warming leads to a continuous rise in the earth's temperature, causing climate change and in turn affecting the water cycle. The distribution of water in the world is subsequently affected.


Every step in treating drinking water and wastewater utilises energy and generates massive volumes of carbon dioxide. In other words, as water use increases, carbon emissions also increase.
Drinking water is sterilised and filtered before transporting to consumers, requiring electricity.
Water is transported to the water service reservoir and then to residential water tanks by powerful water pumps, which are powered by electricity.
Wastewater is transported via sewers to the treatment works. Electricity is needed for transporting and treating wastewater.
596 grams of carbon dioxide are produced in treating 1 cubic metre of drinking water and wastewater!
Global warming increases temperatures and evapotranspiration. The capacity for storing water vapour in the air also increases. Hence natural phenomena (such as typhoons and thunderstorms) arising from water vapour become more frequent and severe.
Global warming leads to the melting of icecaps and glaciers, affecting water flows in some rivers and the overall water cycle. Droughts and floods may occur in some areas.
Global warming brings along climate change and alters the water cycle. Precipitation, river flows and groundwater are all affected across the world.
Hong Kong's average temperature rose by an average of 0.15oC per decade from 1987 to 2016.Six were after the year 2000. Hong Kong is clearly under the influence of global warming.

Temperature rise impacts water evaporation as well as precipitation. Rainfall in recent years became unstable in Hong Kong; of the 20 years with the highest recorded rainfall, six were after the year 2000.

However, high rainfall does not mean that there is sufficient drinking water. Take the six years with high rainfall records as example: precipitation was concentrated in the period from June to August. Large amounts of precipitation within a short period of time only led to reservoirs overflowing, and not all water could be the other hand, of the 20 years with the lowest recorded rainfall, three were after the year 2000.

Therefore, it can be seen that under the impact of global warming, precipitation in Hong Kong has become more extreme. We are now dependent on water supplies from the Dongjiang river. Nevertheless, global warming and climate change also occur in our neighbouring Dongjiang area. In other words, global warming is affecting Hong Kong's water supplies.