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Mr CL Wong (WSD): “We have been using seawater for flushing in Hong Kong since the late 1950s”

  • Mr CL Wong (WSD): “We have been using seawater for flushing in Hong Kong since the late 1950s”

About the entity

Water Supplies Department (WSD)
Water Supplies Department, the Government of the Hong Kong Special Administrative Region of the People’s Republic of China.

Published in:

SWM Bimonthly frontpage

Hong Kong's water supply is an indispensable part of the livelihood of its residents and critical to the territory's sustainable development. The Water Supplies Department provides a reliable supply of quality water to about 7.5 million people.

With careful long-term planning and a balance of demand management and supply management initiatives, Hong Kong has overcome numerous challenges and ensured water security, despite having no natural lakes, major rivers or significant groundwater sources. We interview Mr CL Wong, Director of Water Supplies at Hong Kong’s Water Supplies Department, to learn about some of the innovative schemes they have applied throughout the years and what their plans are into the future.

Q: Firstly, we would like to know briefly your career path and your current role in the Hong Kong Water Supplies Department.

A: After graduating from the University, I worked in an engineering consultant for six years before joining the Water Supplies Department (WSD) of the Hong Kong Special Administrative Region Government (HKSARG) in 1989 as a waterworks engineer. I have worked in different divisions in WSD on all facets of water supply including water resources planning (including importation of Dongjiang raw water), planning, design and construction of water infrastructures, consultants and contract management, asset management, operation and maintenance of water supply and distribution systems, water loss management, etc. In 2013, I was seconded to the Development Bureau of the HKSARG to work as Principal Assistant Secretary to oversee various works policies covering inter alia water supply and flood prevention. I was then promoted to the Deputy Director of Water Supplies in 2015 and subsequently appointed as the Director of Water Supplies in 2017.

People in Hong Kong are now more aware of the importance of water conservation as revealed by the public opinion survey in 2015/16

As the head of WSD, I am responsible for overseeing the operation of WSD and in particular driving its excellence in providing a safe, adequate and reliable water supply to a cosmopolitan city with a population of about 7.5 million. To this end, we are determined to take forward several major initiatives on drinking water safety, water security by developing new water resources such as seawater desalination and recycled water, water conservation by the implementation of various education/publicity programmes, water loss management and use of lower grade water (seawater and recycled water) for non-potable purposes, and system reliability through asset management.

Q: Hong Kong is implementing a water supply structure using different sources: local yield, seawater for flushing, Dongjiang water, seawater desalination, reclaimed water, greywater reuse and rainwater harvesting. How much does each one of them contribute to the drinking water supply and to non-potable uses? To what extent does the Total Water Management strategy consider the carbon footprint of different sources?

A: In 2008, the HKSARG promulgated the Total Water Management Strategy (the Strategy) with a view to ensuring water sustainability in Hong Kong. In 2019, we completed a review and updated the Strategy (namely Strategy 2019) to adopt a two-pronged approach, with emphasis on containing water demand growth and building resilience in the water supply to cater for the extreme effects of climate change with diversified water resources. The key initiatives of the Strategy 2019 regarding water resources include expansion of the use of lower grade water (seawater and recycled water) for non-potable purposes and construction of the first stage of Tseung Kwan O Desalination Plant to build resilience in the water supply. The water resources in Hong Kong will comprise:

  • Dongjiang (DJ) water imported from Guangdong in Mainland China (~45% - 60% depending on the amount of local yield)
  • Local yield (~10% - 25%)
  • Desalinated water (~5%)
  • Seawater and recycled water (including reclaimed water, treated greywater and harvested rainwater) for non-potable uses (~25%)

In the process of reviewing the Strategy, our consultants have set up a panel of international experts to evaluate carefully the different water supply and demand management options including the development of different water resources using an approach of "Multi-Criteria Evaluation" under three sets of criteria: resilience, economics and sustainability with details as follows:

  • Resilience refers to the degree of dependency of an option on future uncertainties and the extent of its contribution to the diversity of water resources.
  • Economics refers to capital and recurrent costs, and life-cycle unit cost of an option and the extent to which it can be implemented progressively.
  • Sustainability refers to environmental impacts such as air quality, marine water quality, biodiversity and atmospheric pollution through greenhouse gas emissions of an option.

The carbon footprints of the different management options have been evaluated under the “Sustainability” criterion in the formulation of the updated Strategy 2019.

We will review the Strategy 2019 in a timely manner and update it including the proportions of different water resources when appropriate to cope with the changes of different factors, including water demand, the effect of climate change on local yield, as well as the cost-effectiveness, technology development, reliability and impacts on the environment of various water resources, etc.

Key initiatives are the use of lower grade water for non-potable purposes and the construction of the Tseung Kwan O Desalination Plant

Q: How effective do you think are your efforts to raise awareness about water conservation among domestic, commercial, and industrial users? How has the average per capita water consumption evolved in the past few years?

A: With our sustained publicity and public education programmes, people in Hong Kong are now more aware of the importance of water conservation as revealed by the public opinion survey in 2015/16. From the survey, 98.2% of the interviewees have implemented one or more water conservation measures (e.g. taking showers instead of baths, shortening the showering time and reducing the flow of shower for bathing and water tap, etc.).

We strengthen the culture of water conservation in Hong Kong through proactive promotion, education and community engagement

Moreover, we continue to strengthen the culture of water conservation in Hong Kong through proactive promotion, education and engagement with the community. So far, we have launched the “Cherish Water Campus” Integrated Education Programme for primary schools and kindergartens aiming at broadening students’ knowledge about water resources, and raising awareness of water conservation and water sustainability via integrating theory with practice, such as school water audit, home water audit and education camp on water conservation. We have also launched a Cherish Water Ambassador Scheme for youngsters. An array of events is tailor-made for these Ambassadors, including Water Treatment Works Guided Tours, short film production workshop and training camp, video competition and in-school promotional activities to educate the Ambassadors on the importance of cherishing water resources and fulfilling and publicising the habits of cherishing water. We have also commissioned a water resources education centre in Tin Shui Wai to enhance public understanding of water resources and water conservation. Since 2014, we launched a territory-wide public activity, “Let’s Save 10L Water” Campaign, to encourage the public to pledge to save 10 litres of water every day and implement water-saving practices in daily lives. For businesses and industries, we continue to promote the “Best Practice Guidelines on Water Usage” to high water consumption industries including catering and hotel sectors in order to enhance water efficiency. We believe the above initiatives will further raise awareness about water conservation among domestic, commercial and industrial users.

The per capita freshwater consumption (pcc) in Hong Kong was contained at 132.6m3 in 2019 as compared to 133.4 m3 in 2016. We have set our goal to reduce the pcc to about 120 m3 by 2030 (i.e. 10% reduction as compared to the baseline in 2016). We aim to achieve the goal through water demand management measures, namely water conservation, water loss management and expansion of the use of lower grade water for non-potable purposes. 

Q: You have implemented innovative schemes to allocate lower grade water to non-potable uses. To what extent are initiatives such as the use of seawater for toilet flushing or greywater reuse cost-effective in comparison with other strategies?

A: Thanks to the innovative idea of our predecessors to save the precious freshwater resource, we have been using seawater for flushing in Hong Kong since the late 1950s. Up till now, Hong Kong is one of the few places in the world extensively applying seawater for flushing. The use of such a sustainable water resource plays an important role in Hong Kong’s water resource management. Currently, a total of 280 million cubic metres (mcm) per annum of seawater is supplied for flushing, conserving an equivalent amount of freshwater which is about 20% of the total water consumption in Hong Kong. It also helps keep the domestic pcc at a relatively low level of around 130 litres per day as compared to other places in the world. Supply of seawater for flushing only requires pumping and minimal treatment, and; thus its cost is much lower than that of the freshwater.

Currently, the existing seawater supply network has already covered 85% of the population in Hong Kong.

280 mcm per annum of seawater is supplied for flushing, conserving an equivalent amount of freshwater, 20% of total consumption

Notwithstanding this, we continue to look for other options to tackle these situations. Anderson Road Quarry Site development is one of such areas situated at high altitude and far which makes the supply of seawater for flushing not favourable in terms of pumping requirement and cost-effectiveness. After evaluation, we have decided to pilot the application of a for collecting grey water in the development for treatment and supplying the treated grey water back to the development for flushing and other non-potable uses to save precious freshwater resource

As one of our missions, we will continue to review the expansion of the supply of lower grade water (seawater and recycled water) to other areas that still use freshwater for flushing where it is technically feasible and cost-effective to do so.

Q: You have pioneered water demand management: water conservation, water loss management, and use of lower grade water for non-potable purposes to an extent right now unthinkable in other developed regions of the world. To what extent have these different strategies been successful? Do you think in the future you will reach a ceiling in water efficiency?

A: The freshwater consumption in Hong Kong has been contained at around 1,000 mcm over the past ten years notwithstanding the continuous growth of population at a rate of 0.7% per annum as well as the economic growth, demonstrating the effectiveness of the water demand management measures implemented in Hong Kong. We believe the following series of water demand management measures have achieved significant results:

  • The sustained publicity and public education programmes have made people more aware of the importance of water conservation as revealed by the public opinion survey in 2015/16.
  • We launched a voluntary Water Efficiency Labelling Scheme in phases since 2009, and; it now covers six major plumbing fixtures and devices. Besides, we have taken one-step further to mandate the use of plumbing products of certain water efficiency grade(s) in new plumbing installations since February 2017.
  • We commenced the Replacement and Rehabilitation (R&R) of Water Mains Programme in 2000 and have substantially completed it in 2015. About 3,000 kilometres of aged water mains (out of the total 8,000 kilometres water mains in Hong Kong) have been replaced and rehabilitated. It brought about a significant reduction in the number of water mains bursts by 96%, from the peak of about 2,500 in 2000 to less than 100 in 2019 and the leakage rate in government water mains from about 25% in 2000 to about 15% in 2019.
  • With the improvement of the water supply network achieved by R&R and making use of sensors, telemetry, network management software and data analysis, we are implementing Water Intelligent Network (WIN) for monitoring the water loss of the freshwater distribution network for follow up action. The WIN strategy was formulated in 2014 and the associated works for its progressive establishment are in progress.
  • We have been expanding the supply of lower grade water (seawater and recycled water) to replace freshwater for non-potable purposes.
  • We have also taken a host of measures to tackle the water loss in private communal water mains under the responsibility of the property owners or property management agents. These measures include installing master meters for housing estates to monitor their water losses and request the property owners and property management agents of those housing estates identified with water loss to take rectification actions, with technical advice provided to them regarding leak detection and repair of the leaking water mains. We are also exploring imposing water charges on property owners for the water loss in their housing estates to provide an economic incentive for them to take prompt rectification action to curb the water loss.

Despite our above achievements up to now, we are not complacent. Instead, webelieve there is still room for further reduction of the pcc in Hong Kong. As mentioned in the reply to Question (3) above, we have set our goal to reduce the pcc to about 120 m3 by 2030 (i.e. 10% reduction as compared to the baseline in 2016) through various water demand management measures.

Q: The risk of water main leakage is high in Hong Kong due to the hilly terrain and other factors. Can you tell us about the use of advanced technology to manage water losses?

A: We are establishing WIN for monitoring and managing the water loss in our freshwater distribution network in a smart manner.

The concept of WIN is basically “Divide & Conquer”. It monitors the network performance in a holistic and continuous manner. Discrete District Metering Areas (DMAs) of manageable size are established in the freshwater distribution network with monitoring and sensing equipment installed in each DMA. Through the continuous monitoring of the flow, pressure and consumption in the DMAs, we could identify those DMAs with water loss and prioritise them for follow up actions according to their amount of water loss. Follow up actions could include active leakage detection, pressure management, speedy repair of water main leaks as well as replacement and rehabilitation of water mains, etc. according to the water loss situation in the DMA. As for DMA where there is room for pressure management without affecting the normal supply, it will also serve as Pressure Management Area (PMA) by the installation of pressure reducing valve(s) to reduce the water supply pressure, and hence the water loss in the area.

Supply of seawater for flushing only requires pumping and minimal treatment, and; thus its cost is much lower than that of the freshwater

We will establish about 2 400 DMAs in our freshwater distribution network over the territory. As of end 2019, WSD has already set up about 1 350 DMAs. In addition, we are installing a Water Intelligent Network Management System (INMS) to assist in consolidating the vast amount of network data from the DMAs and analysing their water loss to identify those DMAs with water loss and prioritise them for follow up actions. The INMS will be commissioned this year while the establishment of the entire WIN will be completed in 2024. While the WIN is still being established and the INMS is being installed, WSD has made use of some of the established DMAs and detected some major leaks in the freshwater distribution mains for repair to curb the water loss.

Q: You have turned to desalination as a way to build resilience in the freshwater supply. Can you explain a bit your plans to address the challenges brought by climate change such as changes in water resource availability and sea-level rise?

A: To enhance water security in adapting to climate change, the review of the Strategy has evaluated the possible impact under the effect of climate change and recommended building resilience in the freshwater supply in Hong Kong.

Under the climate change effect on mean rainfall of the medium-low and medium-high greenhouse gas concentration scenarios, the current supply arrangement with local yield, Dongjiang water and seawater for flushing will be able to cope with the demand up to 2040 provided that water demand management measures are effective to reduce the average freshwater pcc by 10%.

Freshwater use has been contained at 1 000 mcm over 10 years notwithstanding a 0.7% population growth rate per annum and economic growth

However, there is uncertainty about the impact of climate change. The rainfall in Hong Kong may deviate from the above predicted mean rainfall under the climate change effect. Besides, other greenhouse gas concentration scenarios may also occur. There is thus the possibility that the local yield may decrease substantially due to climate change. The Strategy 2019, therefore, recommends building resilience in our freshwater supply. To cater to the lower bound of the envelope of projected effect on local rainfall due to climate change, we are building the resilience through the first stage of Tseung Kwan O Desalination Plant. In the construction of the seawall and associated marine facilities and structures for the desalination plant, the contractor is required to provide adequate preventive measures to avoid any adverse effects on the plant from wave overtopping taking into account the effect of climate change.

If the situation deviates from the present projections due to reasons such as higher-than-expected population growth, the worse-than-projected impact of climate change on rainfall or less-than-anticipated effect of containing water demand growth, we still have the capabilities to overcome the challenges by the implementation of a list of backup options to ensure water security in Hong Kong. They include implementation of the second stage of Tseung Kwan O Desalination Plant, reactivation of mothballed water treatment works, expansion of storage capacity of the Plover Cove Reservoir and water gathering grounds, implementation of other desalination plants and increase of Dongjiang water supply.

Q: Many territories across the world are implementing water supply management initiatives, but few are as advanced as Hong Kong regarding water demand management. Why do you think this is? What is your advice to other jurisdictions considering a variety of strategies to ensure water security in terms of prioritising these two different sides of the water balance?

A: Hong Kong does not have natural lakes, major rivers or substantial underground water sources. With its large population, the per capita water resources in Hong Kong is very low by any standards. Hong Kong has been striving to tackle the water shortage problem. With the great work and innovation of our predecessors including the construction of impounding reservoirs with the two large scale Plover Cove and High Island Reservoir built in the sea, use of seawater for flushing and importation of Dongjiang water from Guangdong in Mainland China, Hong Kong has been enjoying a stable and reliable water supply in the past several decades. While our work on water resources has never stopped, we considered that the continuous increase in water supply to meet the demand was not sustainable. We, therefore, promulgated the Total Water Management Strategy in 2008 aiming to use the precious water resources wisely and in a sustainable manner. The Strategy put emphasis on containing the growth of water demand through the introduction of a host of water demand initiatives which we have been actively implemented in the past decade.

Freshwater resources are limited on earth and could be dwindling due to pollution by human activities. The situation is further stressed with the exponential growth in population. We must manage our water resources in a sustainable way through looking at the two sides of the balance on both the demand and supply for the continuous well-being of mankind.

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