Hong Kong skyline. Credit Colin Wade. Copyright Arup/Wade.

+ Hong Kong relies almost entirely on importing water from Guangdong, a region still recovering from severe droughts in 2009.

Densely populated Hong Kong relies almost entirely on importing water from Guangdong Province in southern China. Even as Guangdong has been ravaged by drought in recent years, it has continued to send two million cubic metres of Pearl River water to Hong Kong every day – where no restrictions on water use have been in force.

As part of the Arup team that entered IMechE’s ‘The Population Challenge' competition, I’ve been looking at how Hong Kong can break this dependence and provide its own sustainable water supply. The good news is that we identified lots of opportunities for Hong Kong to become more self-sufficient. By improving water efficiency and using untapped natural resources, the region can become less reliant on water from southern China and develop its own sustainable supply.

Opportunities for sourcing water in Hong Kong include groundwater, rainwater, seawater and reclaimed water. While each could contribute, some (such as seawater desalination) are expensive and energy-intensive. It’s a question of balancing the potential resource against cost and sustainability.

Against these criteria, rainwater is undoubtedly the most promising opportunity. Hong Kong’s high rainfall (which is predicted to increase) means that harvesting rainwater that falls on buildings can provide a sustainable supply of clean water. A pilot project at the Hongkong Electric Company is reusing more than 100,000m3 of rainwater and wastewater, saving the same amount of fresh water each year.

But rainwater harvesting alone isn’t enough to solve the region’s water supply issues – because some of the supply never reaches people’s taps. In 2010, the reported mains leakage rate was 20%. Simply replacing old water mains – as is currently happening – won’t be enough.

Pressure management could help. By adjusting the water supply pressure to the appropriate level in each area could significantly reduce leakage, without affecting domestic use. In the Philippines, pressure management has helped to reduce non-revenue water to less than 15% in the East Zone of Metro Manila.

Our investigation concluded that managing leaks and harvesting rainwater are Hong Kong’s most effective options for creating a sustainable water supply. The alternative is to rely on taking water from the Pearl River across the border in Guangdong. And that region has barely enough as it is – droughts in 2009 shrivelled up 55,000 hectares of farmland and left at least 55,000 people short of drinking water.

Tags: urbanisation, China, resources, water