Case study of water supply and sanitation infrastructure: Hong Kong

By Matt Burdett, 26 February 2019

On this page, we look at Hong Kong as a case study of infrastructure growth over time in one city. This page is part of a series on Hong Kong’s infrastructure that includes international links, transport, telecommunications, energy and water and sanitation.

  • Tai Tam Reservoir, Hong Kong. The city’s growth has led to the creation of much larger rain-fed reservoirs than this.

Water in Hong Kong

Hong Kong is a relatively small territory which has no adequate sources of water from underground, natural lakes or large rivers. As a result, the infrastructure to supply Hong Kong with drinking water has been extensively designed to minimise the amount of water required, and to ensure an adequate supply can be maintained. Part of this water saving comes from the use of seawater to flush toilets, leaving more fresh water for drinking.

Water supply in Hong Kong

Hong Kong has an extensive system of piped water supplies. These water supplies are largely organised geographically from major water sources such as the two main reservoirs of Plover Cove and High Island, to major centres of population. However, as the map below shows, it is not a linear system: instead, water can be piped around the network to allow for periods when different water sources are not available. This increases the resilience of the system.

Problem: Not enough water

However, as the map above shows, only some areas of Hong Kong are suitable water gathering grounds. Other areas are too flat or the surface runoff flows directly into streams leading straight into the sea. The lack of suitable land to collect water adds to another problem: the rainfall in Hong Kong is highly variable on an annual basis. The graph below shows how the amount of water collected within Hong Kong can vary by up to 300% per year. A further problem is the intensity of the demand compared to the supply. More than 7 million people require over 920 million cubic metres of water per year, of which less than a third can be met by local yield (Water Supplies Department, 2017b).

Solution 1: Dam the sea

Owing to the lack of available land, Hong Kong has built two major reservoirs in the sea: Plover Cove and High Island.

Plover Cove was built in 1967. This extensive project involved the closing of a coastal inlet by building a dam wall over 1km long across the bay. In 1973 the dam wall was raised to create a greater capacity of 230 million cubic metres . The scheme worked so well that in 1978 the High Island Reservoir was built with a capacity of 281 million cubic metres (Information Services Department, 2015). High Island Reservoir was an even more ambitious project, involving the creation of two dams (the West Dam and the longer East Dam) to connect an island to the mainland.

  • Plover Cove dam wall. To the right is the sea; to the left is the reservoir. The dam wall is over 1km long.

Solution 2: Import water

The solution to this water shortage is to import water from mainland China. Since 1965, Hong Kong has imported water directly from the Dongjiang River Basin, which now makes up more than two-thirds of its total supply (Water Supplies Department, 2017b). Water is removed from the Dong River and its tributaries and transported in a series of open canals, tunnels and aqueducts to a pumping station in Hong Kong where it is distributed into ‘holding reservoirs’ such as Kowloon Reservoir and stored until needed.

  • The network of aqueducts, canals, tunnels and pipes that transport water from the Dongjiang River Basin to Hong Kong. Source: Water Supplies Department, 2017.

Solution 3: Use seawater to flush toilets

Hong Kong is very rare: the majority of toilets are flushed with seawater. Water from the sea is purified and filtered, but not to the same standard as drinking water. This conserves freshwater to be used for drinking, cooking, cleaning and other domestic and industrial processes. Around 85% of the population is covered (see map below) with the remaining 15% being too far from the sea for it to be economical to connect them to the sea water supply (Water Supplies Department, 2018).

  • Areas of Hong Kong covered by flushing sea water. The orange and purple areas combine to reach over 85% of the population. Source: Water Supplies Department, 2018.


Hong Kong has an extensive sewerage system to deal with the sewage created by over 7 million people. The following facts are taken directly from the 2017-18 Sustainability Report of the Drainage Services Department (2018):

  • “Treatment of about 2.8 million cubic metres of sewage on average every day and 1,007 million cubic metres of sewage in total in the year
  • “Total length of sewerage network 1,770 (kilometres)
  • “Coverage of public sewerage 93.5% (Population percentage)
  • “About 380,000 tonnes of sludge collected and treated in the year
  • “A total of 314 DSD owned sewage treatment facilities”

Hong Kong has 21 water treatment works which clean water to add back into the drinking water supply (GovHK, 2019). The map below shows how these facilities are distributed throughout the territory, but they are especially common in areas of high population.

Harbour Area Treatment Scheme (HATS)

Hong Kong’s famous harbour and skyline are part of its global appeal. However, by the 1990s, the discharge of sewage into the sea was causing the harbour to become unpleasant with odour, visual pollution and the possible build up of potentially dangerous bacteria such as E.coli (Environmental Protection Department, 2014).

The solution to this problem was the Harbour Area Treatment Scheme (HATS). HATS is a system of tunnels that carry human waste away from the harbour to a treatment facility on Stonecutters Island, several kilometres from the harbour. Stage 1 of the scheme was begun in 2001, with Stage 2A completed in 2015 (Drainage Services Department, 2018). (Note: Stage 2B has not yet taken place at the time of writing, and is not considered an urgent priority.) The map below shows the locations of the tunnels. The green lines show the 23.6 kilometres of tunnels that take 75% of the sewage previously dumped in the harbour to the treatment facility. The red lines show the 21 kilometres of tunnels taking the other 25% of waste (GovHK, 2018).


Drainage Services Department, 2018. Sustainability Report 2017-18: Overview of Sewage Treatment and Sewerage System in 2017-18.

Environmental Protection Department, 2014. FAQS.

GovHK, 2018. Harbour Area Treatment Scheme.

GovHK, 2019. Drinking Water Quality in Hong Kong.

Information Services Department, 2015. Hong Kong – The Facts: Water, Power and Gas Supplies.

Water Supplies Department, 2017. Dongjiang Water.

Water Supplies Department, 2017b. Local Yield.

Water Supplies Department, 2018. Seawater for Flushing.

Case study of water supply and sanitation infrastructure: Hong Kong: Learning activities


  1. Describe the human and physical features of Hong Kong that prevent it from gathering all the freshwater it needs within its borders. [3]
  2. Outline the development of Hong Kong’s reservoir infrastructure. [3]
  3. Explain how Hong Kong’s use of seawater for flushing has reduced its need for new sources of drinking water. [3]
  4. Describe the main features of the sanitation infrastructure of Hong Kong. [4]

Other tasks

History meets Geography through water in Hong Kong. Look at these sources (Source 1, Source 2 and Source 3) and evaluate how important the issue of a water supply was to what many consider to be the ultimate end of the British Empire in 1997.

© Matthew Burdett, 2019. All rights reserved.

All secondary material on this site is clearly referenced and may be subject to copyright restrictions by the original authors. All original material on this page is subject to copyright.