Crazy Rich Hong Kong | Dongjiang Water, Reservoirs and the Water Supply Economy begins with a tap that almost always works in a city whose natural rainfall is abundant but unreliable.
Search for “Hong Kong water supply”, “Dongjiang water Hong Kong”, “Hong Kong reservoirs”, “Plover Cove Reservoir”, “High Island Reservoir” or “Hong Kong tap water” and a remarkable regional system appears. In 2025, Hong Kong consumed about 1.075 billion cubic metres of fresh water. Around 819.8 million cubic metres came from the Dongjiang in Guangdong—about 76% of fresh-water consumption.
As of 1 October 2026, Hong Kong’s impounding reservoirs held about 502.96 million cubic metres of water and were around 85.8% full. Plover Cove Reservoir alone held nearly 204 million cubic metres, while High Island Reservoir held about 235 million. The Crazy Rich story is not that Hong Kong has reservoirs. It is that the city learned to combine imported river water, local rainfall, giant reservoirs, treatment works, pumping networks and seawater flushing into a water system reliable enough that rationing now feels like distant history.
Did You Know? Hong Kong Once Had Severe Water Rationing
For much of Hong Kong’s history, reliable 24-hour water was not guaranteed.
Rapid post-war population growth repeatedly pushed local supply beyond what rainfall and reservoirs could safely provide.
Water restrictions became part of ordinary life.
The modern system is impressive precisely because earlier generations knew what scarcity felt like.
Dongjiang Water Changed the City
Hong Kong has imported water from the Dongjiang since 1965.
The river is one of the major tributaries of the Pearl River and supplies water to more than 40 million people across Guangdong and Hong Kong.
For Hong Kong, the Dongjiang solved a fundamental problem:
local rainfall varies too much from year to year to support a dense city reliably on its own.
Why 76% of 2025 Consumption Came from Dongjiang
WSD figures show fresh-water consumption of about 1.075 billion cubic metres in 2025 and Dongjiang supply of 819.8 million cubic metres.
That is roughly 76%.
The number reveals how regional the water system has become.
Hong Kong’s tap water begins partly hundreds of kilometres upstream.
The Journey from River to Tap
Dongjiang water is extracted in Guangdong and conveyed through dedicated aqueduct infrastructure before reaching Shenzhen Reservoir.
From there it crosses the boundary through pipelines to Muk Wu Raw Water Pumping Station in Hong Kong.
Inside Hong Kong, major aqueduct systems route water toward treatment works and designated reservoirs.
The cup of water at home is the end of a cross-border infrastructure chain.
Why a Dedicated Aqueduct Matters
A dedicated Dongjiang transfer system commissioned in 2003 separated the supply route from pollution sources along the Shima River.
That is a crucial water-quality principle.
The cleaner raw water begins, the more robust the treatment system becomes.
Infrastructure protects quality before treatment even starts.
The Current Dongjiang Agreement Runs Through 2026
Hong Kong’s current Dongjiang water supply agreement covers 2024 to 2026.
It provides a minimum annual supply quantity of 615 million cubic metres while maintaining a longer-term average-supply framework.
The agreement gives Hong Kong supply security while allowing actual intake to vary with local yield and reservoir conditions.
Water contracts are climate-risk management.
Local Rainfall Still Matters
Hong Kong received about 2,558.7 millimetres of rainfall in 2025 according to WSD resource data.
Local catchments yielded about 253.62 million cubic metres of water.
Rainfall reduces how much imported water is required and helps fill local reservoirs.
But local yield can vary dramatically.
That volatility is why imported water remains central.
Why Reservoirs Are Time Machines Too
Rain does not fall exactly when the city needs water.
Reservoirs move water through time.
They capture supply during wetter periods and release it during drier ones.
A reservoir is therefore a storage technology converting irregular climate into regular service.
High Island Reservoir: Engineering the Coastline
High Island Reservoir is Hong Kong’s largest reservoir by capacity.
It was created by constructing dams that enclosed a coastal channel and turned a marine area into freshwater storage.
This is one of Hong Kong’s most dramatic examples of engineering geography rather than simply occupying geography.
The landscape became infrastructure.
Plover Cove: A Reservoir in the Sea
Plover Cove Reservoir was the world’s first large reservoir constructed in a sea inlet.
Engineers enclosed the cove and converted it to freshwater storage.
Its present capacity is more than 200 million cubic metres.
Hong Kong solved land scarcity by using coastal form itself as storage space.
Two Reservoirs Hold Most of the Stored Water
On 1 October 2026, High Island Reservoir held about 235.1 million cubic metres and Plover Cove about 204.0 million.
Together they represented the overwhelming majority of Hong Kong’s stored reservoir water.
The system is therefore geographically concentrated in two giant pieces of infrastructure.
Their reliability has city-wide consequences.
85.8% Full in Early October 2026
WSD data for 1 October 2026 showed total impounding-reservoir storage of about 502.96 million cubic metres, roughly 85.82% of capacity.
A high storage level creates resilience going into drier periods.
But reservoir percentage alone does not determine long-term security because future rainfall and imported supply also matter.
Water planning is always forward-looking.
Water Treatment Turns Raw Water into Drinking Water
Raw water cannot simply be pumped from river or reservoir directly into household taps.
Treatment works remove particles, manage microorganisms and adjust water chemistry to meet drinking-water requirements.
Hong Kong conducts monitoring through the supply chain and at consumer taps.
The reliability of drinking water depends on process control, not only source purity.
Why Chlorine Is Used
Disinfection helps control microorganisms that could cause disease.
Residual disinfectant remains in the distribution system to help protect water as it travels through pipes.
The concentration has to be controlled carefully.
Water treatment is chemistry operating at city scale.
The Pipe Network Is the Invisible Reservoir
Once treated, water must move through an extensive network of pumping stations, service reservoirs and mains.
The network stores smaller amounts of water close to users and manages pressure across Hong Kong’s steep terrain.
A mountainous high-rise city is a difficult hydraulic problem.
Gravity helps in some places.
Pumps do the rest.
Why Pressure Management Matters
Water pressure must be high enough to reach users but not so high that pipes leak or burst unnecessarily.
Pressure-management zones help utilities control that trade-off.
Every extra unit of pressure creates more mechanical stress.
Reliable supply is partly the art of using only as much force as necessary.
Water Main Bursts Are an Infrastructure Risk
Older pipes can fail because of corrosion, ground movement, pressure cycles or external damage.
A burst main wastes treated water and can disrupt roads and buildings.
Asset-management programmes therefore inspect, repair and replace pipes before failure where possible.
The cheapest litre of new water is often the litre that never leaks away.
Hong Kong Uses Seawater for Toilet Flushing
One of Hong Kong’s most distinctive water strategies is large-scale use of seawater for flushing.
WSD’s 2024/25 annual data show about 308 million cubic metres of seawater used during 2024, serving around 6.37 million people.
This reduces demand for treated fresh water.
A non-potable use is matched with a non-potable resource.
Why Seawater Flushing Is Clever
Drinking-water treatment is expensive and freshwater is scarce.
Toilet flushing does not require drinking-water quality.
By building a separate seawater network, Hong Kong avoids spending high-quality fresh water on a low-quality requirement.
It is a matching problem:
use the right resource for the right job.
But Dual Networks Are Expensive
The seawater system requires separate pipes, pumping stations and maintenance.
That creates capital cost and operational complexity.
The system works because dense urban development allows infrastructure to serve large numbers of users.
Density makes specialised networks more economical.
Desalination Adds Another Source
Hong Kong’s Tseung Kwan O desalination plant provides a new climate-resilient water source by converting seawater into drinking water using reverse osmosis.
Desalination is energy-intensive compared with rainfall or imported river water.
Its value is reliability.
The ocean does not disappear during a drought.
Why Diversification Matters
A secure water system should not depend on one source behaving perfectly forever.
Hong Kong combines:
- Dongjiang water;
- local rainfall and catchments;
- reservoir storage;
- desalination; and
- seawater flushing for non-potable use.
Each source solves a different part of the risk problem.
Diversity creates resilience.
Climate Change Makes Rainfall Less Comfortable to Predict
Climate change can alter rainfall intensity, drought risk and extreme-weather patterns.
Hong Kong may experience very heavy rain and still face long-term water-security concerns because timing matters.
A storm can deliver huge amounts of water too quickly to capture all of it.
Water abundance and water security are not the same thing.
Smart Water Networks
WSD has been expanding digital monitoring, sensors and smart-network management.
District metering and data analytics can help detect unusual flows and potential leaks earlier.
The pipe becomes a data source.
Infrastructure maintenance shifts from reacting to visible failure toward detecting invisible abnormal behaviour.
Why Water Quality Data Matters
A public water system depends on trust.
Consumers rarely test the water themselves.
They depend on treatment standards, sampling, monitoring and transparent reporting.
Water quality is therefore both a chemical property and an institutional promise.
Hong Kong’s Water History Explains Its Present System
Past droughts drove reservoir expansion.
Local limits drove Dongjiang imports.
Land scarcity drove innovative reservoirs and seawater flushing.
Climate risk is now driving desalination and smarter management.
Infrastructure history is a sequence of constraints answered with new interfaces.
Water and Electricity Are Connected
Pumping, treatment and desalination consume electricity.
Electricity generation also uses water in various processes.
The two utility systems are therefore interdependent.
A city does not have separate infrastructure networks.
It has one mesh of systems that borrow from one another.
Water and the Northern Metropolis
Large new urban districts require new mains, reservoirs, treatment capacity and pressure systems.
The Northern Metropolis therefore creates a water-infrastructure challenge alongside its housing and technology ambitions.
A city expansion is only real when water can arrive before the residents do.
Singapore and Hong Kong: Two Water-Security Models
Singapore uses its Four National Taps: local catchment water, imported water, NEWater and desalination.
Hong Kong relies heavily on Dongjiang imports, local catchment, reservoirs, seawater flushing and growing desalination capacity.
Both cities learned the same lesson from scarcity:
water security requires diversification, engineering and long-term planning.
What Students Can Learn from Water Supply
Geography
Rainfall, catchments, rivers and coastlines shape water options.
Chemistry
Water treatment depends on disinfection, filtration and careful control of dissolved substances.
Physics
Pressure, gravity and pumping determine how water moves through a city.
Economics
Water systems require large fixed infrastructure investment for a service users expect to remain inexpensive and reliable.
Civilisation mechanics
Water is one of civilisation’s deepest substrates: every higher-level system depends on a reliable source before it can function.
Ten Vocabulary Words for Water Infrastructure
1. Catchment
Land area from which rainfall drains toward a reservoir, river or water system.
2. Reservoir
A body of stored water used for supply or other managed purposes.
3. Aqueduct
Infrastructure built to convey water from one location to another.
4. Raw water
Untreated water before purification for drinking.
5. Potable
Safe and suitable for drinking.
6. Desalination
Removing salts from seawater to produce fresh water.
7. Reverse osmosis
A membrane process using pressure to separate water from dissolved salts and other substances.
8. Disinfection
Treatment intended to destroy or control harmful microorganisms.
9. Service reservoir
A local storage facility helping balance supply and pressure within a distribution network.
10. Water security
Reliable access to sufficient, safe water despite changing demand and environmental risks.
Frequently Asked Questions
How much of Hong Kong’s fresh water came from Dongjiang in 2025?
About 819.8 million cubic metres, equivalent to roughly 76% of fresh-water consumption.
How much fresh water did Hong Kong consume in 2025?
About 1.075 billion cubic metres.
How full were Hong Kong’s reservoirs on 1 October 2026?
About 85.82% full, with roughly 502.96 million cubic metres stored.
What are Hong Kong’s two largest reservoirs?
High Island Reservoir and Plover Cove Reservoir.
Why does Hong Kong use seawater for toilets?
It reduces demand for treated freshwater by matching a non-potable use with a separate non-potable supply.
Why is Dongjiang water important?
Hong Kong’s local rainfall yield is too variable to guarantee reliable supply for the whole city, so Dongjiang imports provide a large, dependable regional source.
Helpful Reading Across the Hong Kong Graph
- Crazy Rich Hong Kong | CLP, HK Electric and the Electricity Grid Economy
- Crazy Rich Hong Kong | Northern Metropolis, San Tin Technopole and the New City Economy
- Crazy Rich Hong Kong | Dragon’s Back, Hiking and the Country Parks Economy
- Crazy Rich Hong Kong | Public Housing, HOS and the Housing Ladder Economy
References and Current Sources
- Hong Kong Water Supplies Department, Dongjiang Water.
- Hong Kong Water Supplies Department, Water Resource Data.
- Hong Kong Water Supplies Department, Current Reservoir Storage, updated October 2026.
- Hong Kong Water Supplies Department, 2026/27 Estimates: Fresh Water Consumption and Dongjiang Supply.
Crazy Rich Hong Kong Made Water Ordinary
A tap is one of civilisation’s greatest interfaces.
Turn it, and a regional river, reservoir network, treatment system and thousands of kilometres of infrastructure answer instantly.
Did you know? Water supply becomes truly rich when the engineering is so reliable that a city can forget how precious the resource underneath the tap really is.