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(20 Mar 2022 SCMP) The approach of World Water Day on March 22 serves as a reminder that, worldwide, some 771 million people lack access to safe water. Amid the Covid-19 pandemic and countless other challenges facing humanity, we cannot forget the importance of water conservation as a means to make us more resilient to climate threats.

The approach of World Water Day on March 22 serves as a reminder that, worldwide, some 771 million people lack access to safe water. Amid the Covid-19 pandemic and countless other challenges facing humanity, we cannot forget the importance of water conservation as a means to make us more resilient to climate threats.

The suspension of many economic activities in Hong Kong due to Covid-19 over the past two years has not lowered our fresh water consumption. On the contrary, we set a new record in water usage last year.

Data from the Water Supplies Department shows an increase of 12.8 per cent in water consumption since 2012.

The city consumed 996 million cubic metres of water in 2019, the year before the outbreak of the pandemic. This figure increased to 1,027 million cubic metres in 2020 and 1,055 million cubic metres in 2021. Both levels are the highest on record, largely because of an increase in water use for washing and cleaning.

This worrying scenario is exacerbated by the sharp drop in the amount of water collected in our reservoirs. In 2016, 385 million cubic metres of water was collected by reservoirs. But, last year, that figure was only 202 million cubic metres, representing a 47.5 per cent drop over the past five years.

Climate change affects patterns of precipitation. Hong Kong is getting hotter and dryer; 2021, 2020 and 2019 were the three hottest years since records began, with the annual mean temperature reaching 24.6 degrees, 24.4 degrees and 24.5 degrees Celsius respectively.

The total rainfall in 2021 was 2,307.1mm, which is 4.6 per cent lower than the 10-year average of 2,414.5mm. With the combined challenge of hotter temperatures and reduced precipitation threatening Hong Kong, we must use every opportunity to lower our water consumption. One important step is to speed up the repair of leaking public and private pipes to minimise water wastage.

Another concerns the government. In early 2020, the administration launched a video aimed at educating the public about hand washing to prevent the spread of Covid-19. It advises citizens to rub their hands with soap for at least 20 seconds, which is correct. However, the video fails to recommend turning off the tap while rubbing our hands, meaning that following this advice will waste water.

To get an idea of how much is wasted in 20 seconds, consider this: the average flow rate of a tap is 7 litres per minute. That means 2.33 litres of water is wasted in 20 seconds.

Assuming that half the city’s population follows this practice, and washes their hands three times a day, we can estimate that the total annual water wastage arising from anti-pandemic hand washing is 9.57 million cubic metres. That’s nearly 31 per cent of the increase in water consumption between 2019 and 2020.

Besides this demonstration of excessive water use by the government, there are many other commercial and individual practices that have contributed to avoidable water wastage.

When visiting a restaurant’s kitchen, you will often see water running continuously from taps, mostly for the sake of convenience. Another example is not bothering to turn off the shower while applying soap. A third example is the 7,000 buildings, both residential and commercial, within the seawater supply zone that have not been switched to use seawater for flushing toilets, wasting a total of 27 million cubic metres of freshwater in 2020.

The Dongjiang River provides up to 80 per cent of our water. Last year, it experienced the worst drought since 1963. It would be unrealistic to expect our demand for water from Guangdong to be granted no matter what.

Climate change means water is an ever more precious resource. At the moment, Hong Kong residents pay a relatively low water tariff. But to prevent that from rising sharply and water rationing becoming a regular event in the city, all government departments, businesses and individuals need to pay much greater attention to water conservation.

Edwin Lau

Executive Director, The Green Earth