Home to a population of 7.49 million residents, Hong Kong is faced with the pressure to accommodate for increasing water demands amidst problems of freshwater scarcity. The interesting thing is, Hong Kong is not landlocked; it is located next to the China Sea, and has the proximity and access to a large body of seawater that it is currently under-utilising.
Despite this, Hong Kong is confronted with many other water issues, among which are its freshwater scarcity, water system inefficiency, and overconsumption. Granted, while there are many more water problems and solutions to be explored, the focus of this discussion will largely be based around these three issues as they are closely related.
Hong Kong’s Current Water Supply
Hong Kong is currently operating under a three pronged-water supply system that encompasses local yield (rainfall), seawater for flushing, and imported water. Of Hong Kong’s freshwater supply, a meager 20-30% is obtained from rainfall catchment, whilst the remaining 70-80% is currently imported from the Dongjiang River in China. The freshwater scarcity has resulted in a majority of the freshwater being sourced from outside Hong Kong’s borders, consequently meaning that Hong Kong is now over-reliant on imported water.
Even though rainfall accounts for a small amount of freshwater in Hong Kong, it is a relatively reliable source. With a sub-tropical climate, Hong Kong sees a large flow of precipitation, with an average annual rainfall of 2300mm. 2017 alone saw a total rainfall of 303.64 million cubic metres. A third of the land in Hong Kong has been developed as catchment territory to take advantage of this precipitation, and the collected water is then stored in one of 17 reservoirs. Despite the increased urbanisation in Hong Kong, impervious surface coverage has remained low. Fig 1 shows the impervious surface coverage increase from 37.61% to 37.94% during the 1995-2015 decade.
Even so, this water is not sufficient to meet the demands of local residents. The average per capita per day consumption of water is currently at 224 liters, over twice the global average of 110 liters. Alone, Hong Kong’s rainfall catchment can only effectively supply each resident 84 liters; imported water satisfies the remaining water demands.
Hong Kong currently imports its water under an agreement known as the “package deal lump sum” from the Dongjiang river, the Eastern tributary of the Pearl River Delta. The river runs down the Guangdong province and supplies 2.42 billion cubic metres of water to the Dongguan-Shenzhen region. Of this, Hong Kong receives a set amount annually (820 million cubic metres in 2011), where a supply ceiling is imposed based on an analysis of Hong Kong’s local yield and water demand forecast. Although this is beneficial in terms of water security, Hong Kong rarely consumes all of its allocations, consuming on average only 80%. Regardless of consumption, Hong Kong is charged for the entire water deal ($USD613.7 million for 2019), meaning that there is little incentive for water conservation measures.
Hong Kong’s current involvement in this importing system puts Hong Kong at a disadvantage financially; the governing Dongjiang River Basin Authority (DRBA) which oversees the Dongjiang water supply has not granted Hong Kong observer status, meaning that Hong Kong is not privy to any managerial decisions, and cannot take part in negotiating better water deals. In 2015 alone, the companies overseeing the package deal lump sum gained 46% of its annual revenue from Hong Kong alone. This is yet another reason for Hong Kong to seek its own water supply and lessen their reliance on imported water.
In addition to this, the water system in Hong Kong remains inefficient. 33% of water that enters the mains is lost, either through leakages or non-revenue water (water that is either unmetered or consumed illegally). This costs the government approximately US$173 million annually and is extremely uneconomical. This is primarily due to Hong Kong’s water being piped under high pressure at around 60-80 meter of head to account for the hilly and mountainous terrain. This is compared to other cities such as Singapore and Philadelphia, which transport water at around 30-40 meter of head.
The Saltwater Portfolio
The state of Hong Kong’s current water supply is unsustainable. Hong Kong needs to find a sustainable source of water located within its borders, and decrease inefficiencies to reduce costs and wastage. Taking into account Hong Kong’s geography, a solution to these issues that may be worth considering is the implementation of a saltwater portfolio.
The portfolio would focus on integrating supply-side strategies to expand the existing source of water within Hong Kong, and demand-side strategies that emphasise external management strategies such as green infrastructure and economic reform.
The Saltwater Portfolio: Supply-Side Management
Focusing on supply-side management, Hong Kong should take advantage of its existing seawater supply to replace fresh-water intensive processes. Hong Kong is unique in that it is currently using seawater to provide 80% of its residents with 70-80% of their flushing water; the water is pumped directly from the sea to consumers as illustrated by the schematic Fig 3. This is currently being implemented in specific regions titled ‘seawater supply zones’ highlighted in orange in Fig 4, and has been expanded to the purple zones.
However, comparing Fig 2 and 4 reveals that the expansion zones have high incidents of leakage, further contributing to the existing water system inefficiency. Instead, the seawater supply should be extended to Lantau Island, the island located in Southwest Hong Kong. This is a suitable location to develop seawater pumping stations for two reasons:
- Compared to other areas in Hong Kong, this region has a relatively low incidence of leakages.
- The region has a large population of mangroves and consequently a large supply of brackish water.
The presence of mangroves provides numerous benefits in terms of Hong Kong’s water supply. Mangroves help to facilitate the creation of brackish water through their absorption of freshwater, as well as the mixing of river and seawater at nearby estuaries. As Hong Kong is also moving towards considering wastewater reuse but currently lacking the infrastructure, the additional benefits of mangrove filtration and purification of water will help increase the wastewater reuse culture in Hong Kong.
Providing the flushing water from these brackish water sources instead of pumping water directly from the ocean will provide the advantages of reducing costs of wastewater treatment as well as the risk of salinity corrosion in Hong Kong’s piping systems. As Fig 3 depicts, all wastewater is transported to the same treatment plant. Currently, the ratio of freshwater waste and saltwater waste is 3:1 – a total 25% of salinity. The success of treating this wastewater is due to this ratio. Improving the ratio by lowering this salinity further with brackish water will improve treatment efficiency and cost. Hong Kong’s pipes are also developed to withstand salt corrosion, having an average lifetime of 20 years. In respond to pipe leakage, this lifetime is being extended to approximately 50 years through the use of plastic in pipe materials.
| Advantages | Disadvantages |
• Brackish Water Dilution • Wastewater Reuse Culture • Little Dependence on Weather • Existing Infrastructure – little cost for installation. • High Amenity Value – Constructed areas such as wetland parks and other Ecotourism • Reduction in flood risk and pollution. • Reduction in mangrove population endangerment through increased planting measures. | • Habitat and Ecosystem Impacts • Maintenance and Upkeep • Requires Managerial efficiency between Government Departments (Water Supplies Department, Agriculture, Department, Tourism Department etc.) • Plants may suffer from excess salt shock. |
An alternative method of circumventing these supposed disadvantages would be the construction of artificial wetlands. These wetlands would be modeled off of the existing Hong Kong mangroves and would be slightly altered in terms of the plant species present (plants with high salinity tolerance). The benefits of artificial wetlands are primarily in that they are not geographically constrained, and do not endanger habitats. Treating wastewater using mangrove purification and filtration is also possible, as the mangroves receive the necessary minerals from wastewater, and reduce the necessity for wastewater treatment infrastructure.
There is already precedent with these constructed wetlands. Austria has 5450 artificial wetlands — installed as vertical flow wetlands to achieve higher rates of nitrification. Installing similar models and taking advantage of Hong Kong’s rainy climate should be particularly effective in bypassing Hong Kong’s current wastewater infrastructure as well as freshwater dependency.
The Saltwater Portfolio: Demand-Side Management
Much of the overconsumption of water arises due to two reasons. First, there is increasing trouble with non-revenue water, water that is either improperly metered or consumed illegally. The second is the pricing of water. These two causes will be explored in this section.
Non-revenue water stems largely from the presence of freshwater cooling towers in Hong Kong. A report from the Hong Kong Electrical and Mechanical Services Department found that in 1996 alone, around 12,000 water cooling towers had been discovered, when only 116 had been approved by the Water Supplies Department (WSD).
These freshwater cooling towers are used primarily for industrial, construction and shipping purposes, as well as for air conditioning. The prevalence of these water cooling towers is largely due to the inexperience of the WSD prosecution team, who, in 2014 had a 10% success rate in prosecutions. To combat issues of non-revenue water, the prosecution team needs to be bolstered through training measures, expansion, as well as water main surveillance to sever towers illegally tapping into the water mains. In terms of utilising Hong Kong’s seawater, this prosecution improvement scheme should be implemented alongside a conversion scheme: converting the leaky freshwater cooling towers into properly installed seawater cooling towers.
This scheme can be funded through the implementation of a salt re-use scheme. The residual salt left over from the boiling of the saltwater can be removed and supplied to the Water Supplies Department in exchange for rebates. The salt will then either be used for other commercial purposes, sold, or for the maintenance of the brackish water supply in artificial wetlands.
| Advantages | Disadvantages |
• Reduction in leakages • Reduction in freshwater consumption by up to 16.3% • No risk of legionella due to saltwater • Salt-reuse potential | • Installation needs to be highly localised (away from vulnerable ecosystems) • Risks of corrosion from saltwater • Requires funding |
The main disadvantages of such conversion and training schemes are that there needs to be proper coordination and managerial practices involved. The success of such schemes is largely dependant on the proper allocation of resources. The Hong Kong WSD already suffers from inefficiencies, so Hong Kong should consider the implementation of stricter regulations, or even third-party intervention (although this may not be politically favored). These schemes also require funding, which may arise from either the government or non-profits; if the saltwater portfolio considers the usage of mangroves and/or artificial wetlands, financing can come from the revenue gained as a result of eco-tourism to these sites.
The financial aspects of this saltwater portfolio also have a large impact on the relative success of demand-side management through economic reform. As shown by Fig 5, Hong Kong has one of the cheapest water charges in the world (especially for its status as a developed city). Compared with other cities such as New York and Philadelphia where it costs approximately $USD470 for 100 cubic metres of water, Hong Kong is charging $USD37 for the same amount.
Decreasing water demand is not as simple as changing prices. Water prices in Hong Kong have remained relatively stable for around 30 years due to political reasons. Furthermore, a survey carried out by the WSD in 2015 found that even if water charges were to be increased by 30.3%, only 19.9% of households would consider reducing their water usage. The problem with Hong Kong’s pricing must be solved through reforming its current tariff system.
The tariff system (as shown in Fig 6) implemented for freshwater consumption is relatively low, as it has not been changed since the late 90s also primarily due to political tensions between Hong Kong and China; the tariff system has also not changed in order for water to remain accessible for a population in which 14% live below the poverty line. Although the tariff is an increasing block system, Fig 6 depicts the first 12 cubic metres of freshwater consumed and the first 30 cubic metres of freshwater flushing water being provided free for all households. The increased tariffs are also relatively low. This is specifically problematic for Hong Kong, which is already overconsuming its water supply.
The main reasons as to why the water prices and tariff system are so low in Hong Kong are mainly due to the large subsidies that are being put into the water supply. From 2000 to 2015, Hong Kong spent approximately $USD5 Billion to ensure that water remained affordable. What this looks like to the average 3-person household is $USD230 in taxation in addition to water utility bills.
To reform this tariff system without changing water prices, the free allocation of water would have to be reduced or removed for all except for the financially disadvantaged. This will be to maintain water equity and access. Specific difficulties that may arise from this decision would be in proving who specifically receives this free allocation, and what constitutes being “financially disadvantaged.” However, even if there are instances of individuals hiding their income to receive this free allocation, for the majority of the population, freshwater consumption would still decrease. Relevant regulations and restrictions would also need to be considered.
Alternatively, seawater could be made more attractive. Diverting a portion of the government subsidies towards the installation of seawater pumping stations and the conservation of mangroves would make this saltwater portfolio more feasible, and consequently more accessible. The free allocation for freshwater flushing should also be removed so that there is a higher incentive for households to convert their flushing water to seawater.
Obviously, the plans for a saltwater portfolio require a high degree of fine-tuning in conjunction with the various Hong Kong departments and Chinese authorities. To lessen Hong Kong’s freshwater consumption and move away from relying on the Dongjiang River, the saltwater portfolio is a solution that will expand the existing water supply within Hong Kong. Through the supply and demand-side management from this portfolio, not only will freshwater demand decrease, but the local yield will also increase. Combined, this will lower the supply ceiling, reducing the imported quantity accordingly so that all of the allocations are used.
Hong Kong is currently considering alternative methods of water supply such as desalination; a desalination plant has begun construction in 2018, however, this is largely inefficient as it will only be able to provide 5% of Hong Kong’s freshwater demand and operate during drought periods. To this end, water planning and resources should be diverted to alternative methods. Moving forward, smarter use of Hong Kong’s saltwater potential is necessary and possible.
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