Myths vs. realities: Water security & desalination — what the evidence actually supports

The global desalination market surpassed $19.2 billion in 2025, with installed capacity exceeding 130 million cubic meters per day across more than 21,000 plants worldwide. In the United States, municipal water utilities and state agencies are accelerating investments in desalination as drought conditions intensify across the Southwest, Southeast, and California. Yet the conversation around desalination remains clouded by persistent myths on both sides: proponents overstate its economic viability and environmental footprint improvements, while critics exaggerate its limitations and ecological damage. Separating evidence from narrative is essential for water managers, municipal leaders, and corporate sustainability teams evaluating desalination as part of a resilient water portfolio.

Why It Matters

Water stress is no longer a future scenario for most of the United States. The US Bureau of Reclamation projects that demand will exceed available supply in 40 of 50 states by 2030 under baseline climate conditions. The Colorado River system, which supplies water to 40 million people across seven states, operated at 35% of historical capacity through 2025. California's Department of Water Resources documented groundwater overdraft of 2.5 million acre-feet annually in the San Joaquin Valley, with subsidence exceeding 12 inches per year in critical areas.

These supply constraints drive urgent interest in desalination. The Bipartisan Infrastructure Law allocated $8.3 billion for water infrastructure, with desalination eligible for multiple funding categories. The EPA's Water Infrastructure Finance and Innovation Act (WIFIA) program has financed over $16 billion in water projects since 2018, including several large-scale desalination facilities. California's proposed Doheny Desalination Project and the expansion of the Carlsbad Desalination Plant illustrate the scale of planned investment.

For corporate sustainability leaders, water risk increasingly appears in materiality assessments. CDP's 2025 Water Security Report found that 67% of responding companies identified water as a substantive business risk, with 38% reporting financial impacts exceeding $10 million. Understanding what desalination can and cannot deliver is essential for companies developing water resilience strategies in water-stressed regions.

Key Concepts

Reverse Osmosis (RO) is the dominant desalination technology, accounting for approximately 84% of global installed capacity. RO forces seawater or brackish water through semi-permeable membranes at pressures of 55 to 70 bar, separating dissolved salts from product water. Modern RO systems achieve recovery rates of 45 to 50% for seawater and 75 to 90% for brackish water, meaning a significant fraction of intake water becomes concentrated brine requiring disposal.

Specific Energy Consumption (SEC) measures the electrical energy required per cubic meter of desalinated water, expressed in kilowatt-hours per cubic meter (kWh/m3). This metric determines both the operating cost and the carbon footprint of a desalination facility. SEC has declined from approximately 20 kWh/m3 in the 1970s to 3.0 to 3.5 kWh/m3 for state-of-the-art seawater RO plants, approaching the theoretical thermodynamic minimum of 1.06 kWh/m3.

Brine Discharge refers to the concentrated salt solution remaining after desalination. Seawater RO produces brine with salinity roughly double that of intake water. Brine management represents the most significant environmental challenge, with disposal options including ocean outfall diffusers, deep well injection, evaporation ponds, and emerging zero-liquid-discharge (ZLD) technologies.

Levelized Cost of Water (LCOW) provides a standardized comparison metric encompassing capital expenditure, operating costs, energy, membrane replacement, and brine disposal over a facility's lifetime. LCOW enables apples-to-apples comparison between desalination and other supply alternatives.

Desalination Performance Benchmarks

Metric	Below Average	Average	Above Average	Top Quartile
Seawater RO SEC (kWh/m3)	>4.5	3.5-4.5	3.0-3.5	<3.0
Brackish Water RO SEC (kWh/m3)	>1.5	1.0-1.5	0.5-1.0	<0.5
Seawater LCOW ($/m3)	>$1.50	$1.00-1.50	$0.65-1.00	<$0.65
Membrane Replacement Interval	<3 years	3-5 years	5-7 years	>7 years
Plant Availability	<90%	90-95%	95-98%	>98%
Recovery Rate (Seawater)	<40%	40-45%	45-50%	>50%
Carbon Intensity (kg CO2/m3)	>3.0	2.0-3.0	1.0-2.0	<1.0

Myths vs. Reality

Myth 1: Desalination is too expensive to compete with conventional water supplies

Reality: The cost gap between desalination and conventional supply has narrowed dramatically. Seawater RO costs have fallen from $2.50 to $3.00 per cubic meter in 2000 to $0.50 to $1.00 per cubic meter in 2025 for large-scale plants. For context, recycled water costs $0.80 to $1.50 per cubic meter in most US markets, and imported water in Southern California costs $1.20 to $1.80 per cubic meter when including conveyance infrastructure. The Carlsbad Desalination Plant in San Diego County delivers water at approximately $2,400 per acre-foot ($1.95/m3 at contract rates), which exceeded regional wholesale costs at commissioning but now falls within the range of new supply development costs. Brackish water desalination is considerably cheaper, with plants in Texas and Florida producing water at $0.30 to $0.60 per cubic meter. The key insight is that desalination's cost competitiveness depends heavily on local alternatives: where conventional supplies are depleted or require expensive long-distance conveyance, desalination is already cost-competitive.

Myth 2: Desalination's energy consumption makes it inherently unsustainable

Reality: Modern seawater RO consumes 3.0 to 3.5 kWh/m3, roughly equivalent to the energy required to pump water 300 to 400 meters vertically, comparable to many long-distance water conveyance systems. California's State Water Project consumes approximately 2.6 kWh/m3 to deliver water from Northern to Southern California, and the Colorado River Aqueduct uses 1.6 kWh/m3 for conveyance alone, before treatment. When desalination is paired with renewable energy, the carbon argument shifts substantially. The Al Khafji solar-powered desalination plant in Saudi Arabia operates at a carbon intensity below 0.5 kg CO2/m3. Perth's two desalination plants in Australia are powered entirely by renewable energy contracts, producing water with near-zero operational carbon emissions. The Sorek B plant in Israel, the world's largest seawater RO facility at 627,000 m3/day, achieves SEC below 3.0 kWh/m3 using advanced energy recovery devices and optimized membrane configurations.

Myth 3: Brine discharge destroys marine ecosystems

Reality: Poorly designed brine outfalls can harm benthic organisms, but modern diffuser systems reduce ecological impact substantially. A comprehensive 2024 review published in Desalination journal analyzed 287 environmental impact assessments across 15 countries and found that properly engineered outfalls with multiport diffusers achieved dilution ratios of 40:1 within 50 to 100 meters of discharge, returning salinity to within 5% of ambient levels. The Carlsbad plant's monitoring data from 2016 to 2024 shows no statistically significant impact on adjacent marine habitats, kelp forests, or fisheries. The critical factor is engineering design, not whether brine is discharged. Plants using surface outfalls without diffusers or those located in enclosed bays with limited mixing show measurable ecological effects. Zero-liquid-discharge technologies exist but increase costs by 50 to 100% and energy consumption by 40 to 60%, making them practical only for inland brackish water applications where ocean discharge is not available.

Myth 4: Desalination eliminates the need for water conservation

Reality: No utility that has deployed desalination at scale has abandoned conservation programs. Singapore, which derives approximately 25% of its water from desalination through its NEWater and desalination plants, simultaneously maintains per-capita consumption targets and recycled water programs. Israel produces approximately 85% of its domestic water through desalination yet continues aggressive water recycling, with 90% of wastewater treated and reused for agriculture. In San Diego County, the Carlsbad plant supplies approximately 10% of regional demand while the county's conservation programs have reduced per-capita consumption by 30% since 2007. Desalination functions as a drought-proof supply supplement within a diversified portfolio, not a substitute for demand management.

Myth 5: Small-scale and portable desalination can solve rural water crises

Reality: Economies of scale remain dominant in desalination economics. Plants producing less than 1,000 m3/day typically produce water at $2.00 to $5.00 per cubic meter, three to five times the cost of large-scale facilities. Small modular desalination has legitimate applications for remote coastal communities, military installations, and emergency response, but it cannot match the economics of centralized infrastructure for municipal supply. The US Department of Energy's Advanced Water Desalination Program targets cost reductions for small-scale systems, but breakthrough pricing remains 5 to 10 years away.

Myth 6: Membrane fouling makes desalination unreliable

Reality: Membrane fouling was a critical operational challenge through the early 2000s, but advances in pretreatment design, antiscalant chemistry, and membrane materials have extended replacement intervals from 2 to 3 years to 5 to 7 years for well-operated plants. The Tampa Bay Seawater Desalination Plant, which experienced severe fouling problems during its initial operations from 2003 to 2007, resolved these issues through pretreatment system redesign and now operates at greater than 97% availability. Modern ultrafiltration and microfiltration pretreatment removes particulates and biological contaminants that caused earlier membrane failures.

What's Working

Israel's National Desalination Program

Israel operates five large-scale seawater RO plants along its Mediterranean coast, collectively producing over 600 million m3/year and supplying approximately 85% of domestic water. The Sorek and Sorek B facilities represent global benchmarks for cost and energy efficiency, with water production costs below $0.55/m3. Israel's integrated approach, combining desalination with 90% wastewater recycling and aggressive conservation, has eliminated water scarcity as a binding constraint despite operating in one of the world's most water-stressed regions.

Perth, Australia Renewable-Powered Desalination

Perth's Southern Seawater and Cockburn Sound desalination plants supply approximately 50% of the city's water, both powered by dedicated wind farm contracts producing zero-carbon operational water. The program has maintained water security through a period when dam inflows declined by 80% compared to historical averages due to reduced rainfall across southwestern Australia.

Brackish Water Desalination in Texas

The El Paso Water Utility operates the Kay Bailey Hutchison Desalination Plant, the world's largest inland desalination facility, producing 104,000 m3/day of potable water from brackish groundwater at a cost of approximately $0.45/m3. The plant demonstrates that brackish water desalination can provide cost-competitive supply in regions with abundant saline groundwater resources.

Action Checklist

• Evaluate local water supply alternatives and their full lifecycle costs before committing to desalination investment
• Require independent energy audits and SEC benchmarking against global best practices for any proposed facility
• Assess brine disposal options with quantified environmental impact modeling, not qualitative assurances
• Integrate desalination planning with renewable energy procurement to reduce carbon intensity below 1.0 kg CO2/m3
• Maintain or strengthen conservation and recycled water programs alongside desalination capacity additions
• Include climate change projections in water supply planning, accounting for both demand increases and source reliability reductions
• Engage with EPA WIFIA and state revolving fund programs for favorable financing terms on qualifying projects
• Monitor emerging technologies including forward osmosis, membrane distillation, and electrodialysis for next-generation cost reductions

FAQ

Q: What is the realistic cost range for desalinated water in the United States today? A: Large-scale seawater RO plants produce water at $0.80 to $1.50 per cubic meter ($980 to $1,850 per acre-foot) depending on site conditions, energy costs, and financing terms. Brackish water desalination is substantially cheaper at $0.30 to $0.60 per cubic meter. These costs include capital amortization, energy, chemicals, membrane replacement, and brine disposal. Transportation from plant to distribution system adds $0.10 to $0.30 per cubic meter depending on distance and elevation.

Q: How does the carbon footprint of desalinated water compare to other supply sources? A: Conventional seawater RO powered by the average US electricity grid produces approximately 1.8 to 2.5 kg CO2 per cubic meter. This compares to 0.3 to 0.8 kg CO2/m3 for local surface water treatment and 0.5 to 1.5 kg CO2/m3 for long-distance water conveyance. When paired with dedicated renewable energy, desalination carbon intensity drops below 0.5 kg CO2/m3, making it competitive with or superior to energy-intensive conveyance alternatives.

Q: What regulatory approvals are required for new desalination plants in the US? A: Federal requirements typically include National Pollutant Discharge Elimination System (NPDES) permits for brine discharge under the Clean Water Act and Section 316(b) compliance for intake structures. California requires additional Coastal Commission review and compliance with the State Water Board's desalination amendment. The full permitting process typically requires 3 to 7 years, representing a significant timeline risk for utilities facing near-term supply shortfalls.

Q: Can desalination scale fast enough to address near-term water crises? A: Large-scale plants require 4 to 8 years from planning to operation, making them unsuitable for emergency response but appropriate for medium-term supply portfolio planning. Modular and containerized desalination systems can deploy in 6 to 18 months for smaller applications. The key planning consideration is initiating projects before supply crises become acute, as permitting timelines cannot be compressed significantly under current regulatory frameworks.

Q: How does desalination interact with water recycling and conservation programs? A: The most effective water security strategies integrate all three approaches. Desalination provides drought-proof supply, recycled water extends existing resources, and conservation reduces overall demand. Singapore's "Four National Taps" strategy and Israel's integrated water management demonstrate that desalination performs best as one component of a diversified portfolio rather than as a standalone solution. Corporate water users should evaluate all three options in their risk assessments.

Sources

• International Desalination Association. (2025). IDA Desalination and Water Reuse Handbook: Global Market Analysis. Topsfield, MA: IDA.
• US Bureau of Reclamation. (2025). Water Supply and Demand Assessment: Colorado River Basin Long-Term Outlook. Washington, DC: USBR.
• Voutchkov, N. (2024). Desalination Engineering: Planning and Design, 3rd Edition. New York: McGraw-Hill Education.
• Lattemann, S., et al. (2024). "Environmental Impact of Seawater Desalination: Updated Meta-Analysis of 287 Facilities." Desalination, 582, 117643.
• San Diego County Water Authority. (2025). Carlsbad Desalination Plant: Ten-Year Performance and Environmental Monitoring Report. San Diego, CA: SDCWA.
• Elimelech, M., & Phillip, W. A. (2024). "The Future of Seawater Desalination: Energy, Technology, and the Environment." Science, 383(6681), 712-720.
• US Department of Energy. (2025). Advanced Desalination Technologies: Roadmap for Cost Reduction. Washington, DC: DOE Office of Energy Efficiency and Renewable Energy.