Executive Summary

Singapore’s exploration of a sixth desalination plant, potentially fully underground, represents a pivotal evolution in urban water infrastructure planning. This case study examines the strategic context, innovative solutions, future outlook, and potential impacts of this development on Singapore’s water security and urban planning paradigm.

Background and Strategic Context

The Water Security Imperative

Singapore faces unique water security challenges as a densely populated city-state with limited natural water resources. The country’s current water demand stands at 440 million gallons daily, equivalent to filling 800 Olympic-sized swimming pools. This demand is projected to double by 2065, driven primarily by industrial growth, which is expected to account for over 60% of total water consumption compared to 55% today.

The Republic’s water supply relies on the “Four National Taps” strategy: imported water from Malaysia’s Johor River (the largest source), local catchment rainfall, NEWater (recycled water), and desalination. However, two of these sources are weather-dependent, making them increasingly vulnerable to climate change-induced weather pattern disruptions.

Current Desalination Infrastructure

Since introducing desalination in 2005, Singapore has developed five plants located in coastal areas including Tuas, Jurong Island, and Marina East. These facilities collectively provide 190 million gallons daily, meeting up to 43% of current water demand. The most recent addition, the Keppel Marina East Desalination Plant opened in February 2021, introduced innovations including underground treatment facilities and a green rooftop for community recreation.

The Sixth Desalination Plant: Innovation Overview

Groundbreaking Underground Design

The proposed sixth plant represents a significant engineering leap, with PUB commissioning a 10-month feasibility study to assess the viability of a fully underground desalination facility. This approach would extend beyond the Marina East plant’s partial underground design, potentially setting new global standards for space-efficient water infrastructure.

Three Design Options Under Evaluation

Option 1: Fully Underground Plant This unprecedented design would house all treatment facilities below ground, freeing the entire surface area for recreational facilities, green spaces, or complementary infrastructure. This represents the most ambitious space optimization strategy.

Option 2: Multi-Storey Building Configuration Similar to the Tuas South Desalination Plant, this vertical design would incorporate higher multi-storey buildings to minimize land footprint while maintaining operational efficiency.

Option 3: Enhanced Multi-Level Design This hybrid approach combines multiple levels with deeper basements to house treatment facilities, achieving a lower land footprint than traditional horizontal layouts while remaining less engineering-intensive than the fully underground option.

Dual-Treatment Capability

Following the Marina East model, the plant would possess the flexibility to treat both seawater and fresh water. This adaptability enhances operational resilience, allowing the facility to respond dynamically to weather patterns, source water availability, and demand fluctuations.

Long-Term Solutions and Strategic Approaches

Land Use Optimization in a Land-Scarce Environment

Singapore’s land constraints make every square meter precious. The underground approach addresses multiple challenges simultaneously:

Vertical Integration Strategy: By moving water treatment infrastructure underground, Singapore can pursue true multi-use land development. Surface areas can accommodate parks, sports facilities, community centers, or even commercial developments, effectively doubling or tripling the value derived from each land parcel.

Lessons from Existing Infrastructure: PUB’s study incorporates insights from current facilities, particularly the Marina East plant’s successful integration of treatment facilities with public amenities. The agency is exploring deeper basements and more sophisticated multi-storey configurations that build upon these proven concepts.

Environmental Sensitivity: The tender documents indicate that nature groups may be engaged for environmental impact assessments, suggesting the site’s proximity to sensitive ecological areas. Underground development could minimize surface-level disruption to natural habitats while still providing essential water infrastructure.

Energy Efficiency and Sustainability Solutions

Desalination remains Singapore’s most energy-intensive water production method, making efficiency improvements critical for environmental and economic sustainability.

Integrated Infrastructure Model: The Jurong Island Desalination Plant demonstrates the potential of co-location strategies. By integrating with Tuas Power’s Tembusu Multi-Utilities Complex, it achieves 5% greater energy efficiency than conventional plants through shared seawater intake, discharge facilities, and direct electricity supply. This saves enough energy annually to power nearly 1,000 HDB households.

Future-Proofing for Raw Water Quality: The feasibility study will analyze potential deterioration in raw water quality due to climate change, pollution, or other factors. By anticipating these challenges now, the plant design can incorporate additional treatment processes or flexible systems that adapt to changing source water conditions.

Renewable Energy Integration: While not explicitly mentioned in current plans, underground facilities could potentially integrate with renewable energy sources such as solar panels on surface areas or innovative energy recovery systems within the treatment process itself.

Climate Resilience Architecture

Climate change poses existential risks to water-dependent sources. The dual-treatment capability addresses this directly:

Weather Pattern Adaptation: During periods of abundant rainfall, the plant can process fresh water from reservoirs, reducing energy consumption. During droughts or dry spells, it can shift to seawater desalination, ensuring consistent supply regardless of weather conditions.

Redundancy and System Flexibility: By diversifying treatment capabilities across multiple plants, Singapore builds redundancy into its water system. If one source becomes compromised, others can compensate, preventing supply disruptions.

Meeting 2065 Water Demand Targets

PUB’s strategic goal calls for recycled water and desalination to meet up to 85% of Singapore’s water demand by 2065. Achieving this requires:

Capacity Expansion: The sixth plant will add significant capacity to the existing 190 million gallons daily from desalination. As demand doubles to approximately 880 million gallons daily by 2065, multiple additional facilities will likely be needed.

Technology Advancement: The 40-year timeline allows for incorporating emerging technologies in membrane efficiency, energy recovery, and treatment processes that could dramatically reduce operational costs and environmental impact.

Reduced Import Dependency: Strengthening domestic water production capabilities reduces reliance on Malaysian imports, enhancing sovereignty and negotiating position while building long-term supply security.

Outlook: Future Implications and Developments

Short-Term Outlook (2025-2030)

Feasibility Study Completion: The 10-month study will conclude by late 2025 or early 2026, providing PUB with detailed technical, economic, and environmental assessments of the three design options.

Design Selection and Planning: Following study completion, PUB will likely select a preferred design approach and begin detailed engineering and planning phases. This could extend through 2027-2028, including environmental impact assessments, stakeholder consultations, and regulatory approvals.

Parallel Efficiency Improvements: Existing facilities will continue operating under extended contracts (such as the SingSpring plant’s three-year extension announced in December 2024), while ongoing research focuses on improving energy efficiency and reducing operational costs across all plants.

Household Consumption Targets: Singapore aims to reduce household water consumption from 142 liters per person daily (2024) to 130 liters under the Singapore Green Plan 2030. Success in achieving this target would slightly moderate overall demand growth.

Medium-Term Outlook (2030-2040)

Construction and Commissioning: Assuming design approval by 2028-2029, construction of the sixth plant would likely span 4-6 years, with commissioning possible by the mid-2030s. Underground construction typically requires longer timelines due to geological challenges and complex engineering requirements.

Technology Evolution: Desalination technology is advancing rapidly. By the 2030s, Singapore may incorporate next-generation membranes with higher selectivity and lower energy requirements, advanced materials that resist fouling, and AI-driven operational optimization systems.

Integrated Urban Planning: Success with the sixth plant’s multi-use design could establish a new paradigm for Singapore’s infrastructure development, with subsequent facilities automatically designed for vertical integration with housing, commerce, recreation, and transportation systems.

Regional Climate Impacts: Southeast Asia is experiencing accelerating climate change effects. By the 2030s, Singapore may face more extreme weather events, including prolonged droughts and intense rainfall periods, making the flexible dual-treatment capability increasingly valuable.

Long-Term Outlook (2040-2065)

Additional Capacity Requirements: To meet the 85% target for desalination and recycled water by 2065, Singapore will likely need seventh, eighth, and potentially ninth desalination plants, alongside expanded NEWater capacity. Each new facility will benefit from lessons learned from the sixth plant’s innovative design.

Energy Transition: Singapore’s broader energy transition toward renewable sources and potentially nuclear power will directly impact desalination economics. Lower-carbon, cheaper electricity would make desalination more sustainable and affordable.

Water Demand Management: Industrial processes will likely become more water-efficient through technological innovation and regulatory requirements. Circular economy principles may reduce industrial water consumption growth below current projections.

Malaysian Water Agreement: Singapore’s water agreements with Malaysia extend to 2061 and 2062. As these expiration dates approach, decisions about renewal, renegotiation, or increased self-sufficiency will significantly influence desalination expansion plans.

Global Knowledge Transfer: Singapore’s underground desalination expertise could become a valuable export, assisting other land-scarce, water-stressed cities worldwide in developing similar solutions.

Impact Analysis

Economic Impacts

Capital Investment: Desalination plants require substantial upfront investment. Previous facilities have ranged from hundreds of millions to over a billion dollars depending on capacity and design complexity. The underground option will likely command a premium due to additional engineering challenges, but this is offset by surface land value creation.

Operational Costs: Desalination remains Singapore’s most expensive water production method due to energy intensity. However, efficiency improvements at facilities like Jurong Island demonstrate that innovative design can reduce operational costs by 5% or more, translating to millions in annual savings across the system.

Water Pricing Implications: As desalination capacity grows to meet 85% of demand, water prices may experience upward pressure unless offset by technological improvements. However, the cost of water insecurity far exceeds the cost of desalination investment.

Land Value Creation: By freeing surface land for mixed-use development, the underground approach creates significant economic value. In Singapore’s property market, 2-14 hectares of prime urban land represents hundreds of millions of dollars in development potential for residential, commercial, or recreational purposes.

Industrial Competitiveness: Reliable water supply at stable prices enables industrial growth, particularly for water-intensive sectors like pharmaceuticals, electronics manufacturing, and petrochemicals. This supports Singapore’s position as a regional manufacturing and business hub.

Environmental Impacts

Energy Consumption: Desalination’s primary environmental challenge is its energy demand. At current scale, Singapore’s desalination plants consume enough electricity to power tens of thousands of households. As capacity expands toward 2065, total energy consumption could increase substantially unless offset by efficiency gains.

Carbon Footprint: Energy consumption translates directly to carbon emissions. Meeting the 85% target through desalination and recycled water while achieving carbon neutrality goals will require either dramatic efficiency improvements or transitioning to low-carbon electricity sources.

Marine Ecosystem Effects: Desalination plants intake seawater and discharge concentrated brine. While modern plants minimize impacts through careful design and discharge management, expanding capacity requires ongoing environmental monitoring and mitigation strategies to protect marine life.

Reduced Catchment Pressure: By decreasing reliance on rainwater catchment, Singapore can potentially dedicate more land to natural ecosystems rather than expanding reservoir areas, benefiting biodiversity.

Surface Land Restoration: Underground construction enables surface areas to be designed as green spaces, urban forests, or wetlands, providing ecosystem services, urban cooling, flood management, and biodiversity habitat in otherwise industrial zones.

Social and Community Impacts

Water Security Perception: Visible investments in water infrastructure reinforce public confidence in long-term supply security, reducing anxiety about climate change impacts and geopolitical dependencies.

Recreational Amenities: Multi-use surface development above underground facilities can provide valuable recreational spaces for communities. The Marina East plant’s green rooftop demonstrates this potential, offering parks and community gathering spaces in densely populated areas.

Public Health: Reliable, high-quality water supply is fundamental to public health. Enhanced treatment capabilities, including adaptation to declining raw water quality, protect communities from waterborne diseases and contaminants.

Intergenerational Equity: Investments in long-term water infrastructure demonstrate commitment to future generations, ensuring that Singapore remains livable and economically viable for children and grandchildren despite climate change challenges.

Educational Opportunities: Advanced water facilities serve as platforms for public education about water conservation, sustainable technology, and environmental stewardship, fostering a culture of resource consciousness.

Technological and Innovation Impacts

Engineering Leadership: Successfully constructing a fully underground desalination plant would position Singapore as a global leader in water infrastructure innovation, creating export opportunities for engineering expertise and technological solutions.

Research and Development: The project will drive R&D in areas including underground construction techniques, space-efficient treatment technologies, energy optimization systems, and smart water management platforms.

Spin-off Technologies: Innovations developed for the desalination plant may find applications in other sectors, such as underground construction for data centers, transportation infrastructure, or industrial facilities.

Human Capital Development: Complex infrastructure projects develop highly skilled engineering, construction, and operations workforces, strengthening Singapore’s technical capabilities across industries.

Smart Water Systems: Integration of IoT sensors, AI-driven optimization, and predictive maintenance systems in new facilities contributes to Singapore’s smart city ecosystem, with lessons applicable to energy, transportation, and urban management.

Geopolitical and Strategic Impacts

Water Independence: Reducing reliance on Malaysian water imports strengthens Singapore’s strategic autonomy and resilience against geopolitical pressures or supply disruptions.

Regional Influence: Demonstrating successful water self-sufficiency enhances Singapore’s soft power and positions the nation as a model for other water-stressed cities, particularly in Southeast Asia.

Climate Adaptation Leadership: As climate change intensifies water stress globally, Singapore’s proactive adaptation strategies offer valuable lessons for international partners, strengthening diplomatic relationships through knowledge sharing.

Economic Security: Water security underpins economic security. Reliable water supply protects against economic disruption, maintaining investor confidence and supporting continued growth.

Urban Planning and Development Impacts

Paradigm Shift: The underground approach could fundamentally change how Singapore conceptualizes infrastructure development, moving toward systematic vertical integration of utilities, transportation, and commercial/residential spaces.

Density Management: As Singapore approaches build-out limits in surface development, going underground becomes increasingly attractive for various infrastructure needs, from utilities to storage to transportation.

Precedent Setting: Success with underground desalination establishes technical confidence and regulatory frameworks for subsequent underground developments, accelerating future projects.

Land Use Optimization Models: The multi-use design provides a template for other land-scarce cities worldwide, demonstrating how to maximize value extraction from limited land resources while meeting infrastructure needs.

Community Integration: By co-locating essential infrastructure with community amenities, Singapore can create neighborhoods where industrial, recreational, and residential functions coexist harmoniously, reducing transportation needs and enhancing livability.

Challenges and Risk Considerations

Technical Challenges

Geological Complexity: Underground construction in Singapore faces challenges including variable soil conditions, high water tables, and limited geological depth in some areas. Extensive site investigation and specialized engineering will be required.

Construction Risks: Underground projects involve higher construction risks including flooding, soil stability issues, and confined space challenges. These translate to longer timelines and potentially higher costs.

Maintenance Access: Underground facilities require careful design for maintenance access, equipment replacement, and emergency response. The inability to easily expand or modify underground structures requires precise long-term planning.

Economic Challenges

Cost Overruns: Underground construction is inherently more expensive and prone to cost overruns than surface facilities. Singapore must balance innovation ambitions with fiscal prudence.

Energy Price Volatility: Desalination economics are highly sensitive to energy prices. Fluctuating electricity costs could make operational budgeting challenging and affect water pricing stability.

Technology Obsolescence: The 40-year infrastructure lifespan means designs finalized in 2025-2030 must accommodate technologies that won’t exist until 2050-2065, requiring flexible, adaptable designs.

Environmental Challenges

Marine Impact Scaling: As desalination capacity expands, cumulative impacts on marine ecosystems require careful management. Concentrated facilities or dispersed plants each present different challenges for marine life.

Energy-Water Nexus: Meeting both carbon neutrality and water security goals simultaneously requires coordinated planning across energy and water sectors, complicated by competing priorities and resource constraints.

Social and Governance Challenges

Public Acceptance: Underground infrastructure may face public concerns about safety, maintenance, and transparency. Clear communication and community engagement are essential for social license.

Regulatory Frameworks: Innovative underground development may require new regulatory approaches for safety standards, environmental protection, and land use coordination.

Stakeholder Coordination: Multi-use surface development requires coordination among water, parks, urban planning, transportation, and other agencies, increasing project complexity.

Recommendations

For Policymakers

1. Prioritize Flexibility: Select a design option that accommodates future technology upgrades and capacity expansions without major reconstruction.
2. Integrate Energy Planning: Coordinate desalination expansion with renewable energy development and grid modernization to manage the energy-water nexus strategically.
3. Establish Innovation Incentives: Create frameworks that encourage continuous improvement in desalination efficiency and sustainability across all facilities.
4. Enhance Regional Cooperation: While building self-sufficiency, maintain constructive water relationships with Malaysia and explore collaborative regional approaches to water security.

For Industry and Technical Community

1. Invest in R&D: Prioritize research into next-generation membranes, energy recovery systems, and smart operations to drive down operational costs.
2. Share Knowledge: Document and disseminate lessons learned from Singapore’s underground desalination experience to benefit the global water community.
3. Develop Workforce: Build specialized expertise in underground construction, water treatment technology, and integrated infrastructure design.

For Communities and Citizens

1. Embrace Conservation: While infrastructure expands, individual and household water conservation remains critical to managing demand growth and reducing environmental impact.
2. Engage Actively: Participate in consultations about facility design, particularly regarding surface amenity development, to ensure community needs are reflected.
3. Support Innovation: Recognize that ambitious infrastructure projects involve risks and challenges, supporting long-term thinking over short-term cost concerns.

Conclusion

Singapore’s sixth desalination plant represents far more than additional water production capacity. It embodies a sophisticated response to intersecting challenges of climate change, land scarcity, resource security, and urban sustainability. The potential underground design pushes the boundaries of infrastructure engineering while creating new possibilities for multi-use urban development.

The project’s success will depend on careful technical execution, prudent financial management, environmental stewardship, and community engagement. However, the long-term impacts extend well beyond Singapore, offering a model for water-stressed cities worldwide facing similar constraints and climate pressures.

As Singapore pursues water self-sufficiency through innovation, it continues demonstrating that small nations can achieve outsized influence through technological leadership, strategic planning, and bold vision. The sixth desalination plant is not merely infrastructure; it is a statement about Singapore’s commitment to securing its future in an uncertain world, one cubic meter of treated water at a time.