Arizona’s water future may hinge on a choice between two radically different ways of importing moisture into one of the driest regions of the United States: moving seawater inland through a large centralized desalination system, or producing drinking water close to where people live by extracting humidity from the atmosphere. A study by E. Day and P. Westerhoff, published in npj Clean Water, compares these strategies through the lens of Arizona’s growing water stress. The analysis places a familiar megaproject—the proposed use of Sea of Cortez seawater—alongside a more distributed and technologically novel approach: atmospheric water harvesting. The comparison arrives as the state faces intensifying pressure from population growth, prolonged drought, groundwater depletion and a changing climate.
The basic challenge is deceptively simple. Arizona is landlocked, yet some of its most ambitious water-importation concepts depend on reaching the Gulf of California, also known as the Sea of Cortez, in Mexico. A centralized desalination strategy would draw seawater, remove its dissolved salts and impurities, and transport the treated water over long distances and difficult terrain. Desalination itself relies primarily on reverse osmosis, a pressure-driven membrane process that forces water through microscopic barriers while retaining salts, minerals and many contaminants. The result is high-quality freshwater, but the process requires substantial energy, complex infrastructure and a carefully managed plan for disposing of the concentrated brine left behind.
Atmospheric water harvesting works from a different starting point. Instead of importing liquid water from the coast, it captures water vapor already present in the air. Depending on the technology, machines can cool air below its dew point so that vapor condenses into liquid, or use moisture-absorbing materials known as desiccants that release water when heated. The water must then be filtered and disinfected before it can be used. These systems can be deployed in individual buildings, neighborhoods, industrial facilities or remote communities, creating a distributed network rather than a single supply corridor. Their appeal is obvious: no ocean pipeline is required, and water production can occur near the point of demand.
But Arizona’s atmosphere is not an effortless reservoir. Hot desert air can contain surprisingly little moisture, especially during the driest parts of the year. Atmospheric systems therefore face a fundamental thermodynamic penalty: extracting a small quantity of water may require processing a very large volume of air. Cooling-based devices must remove heat while operating in an environment where temperatures are already high, and desiccant systems require energy to regenerate their moisture-absorbing materials. Performance can improve during Arizona’s summer monsoon, when humidity rises, but seasonal variability makes reliable year-round production a central engineering concern.
The study’s comparison is therefore not simply a contest between a giant pipeline and a collection of futuristic machines. It is an examination of how scale changes the environmental and economic character of water supply. A centralized desalination project could produce very large volumes continuously, potentially serving municipal systems and industrial users. However, it would also concentrate risk in a few critical assets: intake facilities, treatment plants, pipelines, pumping stations and cross-border agreements. A failure, disruption or cost overrun at one point in the system could affect a broad service area. Atmospheric water harvesting distributes production across many sites, potentially making the network more resilient to localized failures, but each individual unit produces a comparatively modest amount of water and requires its own maintenance, energy supply and quality monitoring.
Energy is the common denominator linking both strategies. Reverse osmosis desalination is more energy-efficient than older thermal desalination methods because it does not require boiling seawater, but pressurizing water across membranes still consumes electricity. Moving freshwater from the Sea of Cortez to Arizona would add another major energy demand, because pumps must overcome both distance and elevation. The total climate impact would depend heavily on the electricity source. Renewable power could reduce operational emissions, while fossil-fuel-generated electricity could make imported water significantly more carbon-intensive. Atmospheric water harvesting also has an energy profile that varies by climate, device design and operating conditions. In arid air, the electricity required per liter can rise sharply, making efficiency and renewable integration decisive.
Water quality and environmental effects create another set of trade-offs. Desalination produces a concentrated brine stream that must be returned to the marine environment or managed through another disposal method. Poorly designed discharge can alter local salinity and affect marine ecosystems, while seawater intakes can harm small organisms drawn into the treatment system. A long pipeline would also cross landscapes and jurisdictions, raising questions about construction impacts, land access and governance. Atmospheric systems avoid marine brine, but they are not environmentally neutral. They use electricity, may require replacement filters and sorbent materials, and can generate wastewater or concentrated contaminants during treatment. Because these machines operate close to homes and businesses, their maintenance and sanitation practices become part of the public-health equation.
The distributed model could nevertheless change how Arizona thinks about water security. Instead of treating water as a commodity produced far away and delivered through a single regional network, communities could combine atmospheric harvesting with conservation, wastewater recycling, storm-water capture and groundwater management. Small systems might support emergency supplies, remote facilities or buildings with high water needs. They could also reduce pressure on centralized infrastructure during peak demand. Yet distributed does not automatically mean cheap or universally accessible. Equipment costs, electricity prices, humidity conditions and maintenance expertise would determine where atmospheric harvesting is practical. In places with very dry air, the technology may be better suited as a supplemental source than as a replacement for conventional supplies.
The comparison also highlights a political distinction. A Sea of Cortez project would require cooperation across national borders, long-term financing, regulatory approvals and agreements over water rights and environmental responsibility. Its benefits and costs would be distributed across a large region, potentially creating disputes over who pays, who controls the infrastructure and who receives the water. Atmospheric water harvesting can be authorized and installed at a much smaller scale, but thousands of separate systems would require standards for drinking-water quality, electrical safety, reporting and end-of-life disposal. The centralized approach concentrates governance; the distributed approach multiplies it.
Rather than identifying a single technological winner, Day and Westerhoff’s analysis frames Arizona’s water dilemma as a systems-design problem. The key question is not only how much water a technology can produce, but where the water is made, how much energy it consumes, what infrastructure it depends on, how vulnerable it is to disruption and what environmental burdens it creates. Sea of Cortez desalination could offer large-scale production if its energy, ecological and political challenges are resolved. Atmospheric water harvesting could provide flexible local supplies if devices become more efficient and affordable under desert conditions. For Arizona, the most durable strategy may ultimately be a portfolio in which imported, recycled, conserved and locally harvested water reinforce one another rather than compete as isolated solutions.
Subject of Research: Comparison of centralized Sea of Cortez desalination and distributed atmospheric water harvesting strategies for Arizona.
Article Title: Centralized and distributed water importation strategies for Arizona: comparing Sea of Cortez desalination and atmospheric water harvesting.
Article References: Day, E., Westerhoff, P. Centralized and distributed water importation strategies for Arizona: comparing Sea of Cortez desalination and atmospheric water harvesting. npj Clean Water (2026). https://doi.org/10.1038/s41545-026-00620-4
Image Credits: AI Generated
DOI: 10.1038/s41545-026-00620-4
Keywords: Arizona water supply, desalination, Sea of Cortez, atmospheric water harvesting, reverse osmosis, water scarcity, distributed infrastructure, centralized infrastructure, water-energy nexus, climate resilience
