The Western United States is famously dry. Despite a century of large-scale damming and irrigation, vast areas of land throughout California, Nevada, Arizona, Oregon, and New Mexico remains uninhabited and undeveloped. Like 30% of Earth’s surface, it is a desert, comprising enormous tracts of land with almost no ecological productivity or population. In Marc Reisner's Cadillac Desert, the seminal critique of the widespread development of the arid West, it is nature's indifference to water that sets a hard cap on the population — and potential — of America west of the Rockies. 

Fortunately, the builders of the Hoover Dam never read that book, as it was published decades after the dam was constructed. Since the dam’s completion in 1936, the 80 million people who make their home west of the Rocky Mountains have benefited from generations of prosperity earned by its hard-won development and that of many dams like it. California’s world-famous climate, natural resources, and agriculture were unlocked by the delivery of relatively modest volumes of fresh water that were otherwise locked behind a few inconveniently located mountain ranges.

Not 500 feet from where I write this, a century-old pipe 16 feet in diameter channels an underground river hundreds of miles from the Colorado River to Los Angeles, a thriving metropolis with a population and economy larger than Australia’s. The past century of prosperity has produced a culture happily ignorant of this weight-bearing infrastructure — a culture foreign to, if not hostile toward, the idea that humans can positively improve the natural environment. 

Still, as impossible as it would have seemed to the workers who built the Colorado River Aqueduct, the California Aqueduct, and the Los Angeles Aqueduct, our record growth and wealth has now exhausted the water supply they tapped. By the 1970s, the Bureau of Reclamation — a federal agency responsible for managing water and power supply in the West — was forced to concede that there just weren’t any more large rivers short of Alaska that could supply more fresh water to western states. Indeed, the intervening decades have seen a steady increase in temperature and decline in flows, such that full usage of water rights now puts our rivers and aquifers under extreme stress.

In this environment of renewed scarcity, the option to create more fresh water is scarcely mentioned before factions on all sides leap directly into highly politicized, zero-sum, and unproductive fights over allocation. Right now, half of California’s water supply flows back into the environment, 40% goes to agriculture, and just 10% goes to cities. City dwellers and conservationists like to point out that crops like almonds or alfalfa are water-inefficient and that agriculture — while a massive industry — makes up only 2.5% of the state’s GDP.  Farmers, in turn, like to fight back against environmental concessions, and everyone points a finger at lawns, leaks, wastewater, stormwater runoff, Mexican water allocations … the list goes on. 

The goal of exercising dominion over water is not to reduce its consumption to zero, but to productively use it to improve our lives. Directing water away from agriculture reduces consumption, but California has less water and more sun than the Midwest, which makes its harvest particularly vital for access to affordable, fresh food during winter. It is by far the largest agricultural producer in the United States and the fifth largest in the world. Half of the country’s fruits and vegetables are grown here, while more water still supports feed crops for the state’s massive cattle and dairy industries. Affordable food depends on copious quantities of fresh water. So while agriculture isn’t the biggest industry in California, California agriculture has an outsized impact on the nation’s diet. Still, the default response to water scarcity is for officials to force farmers to fallow their farms across the state, maintaining a narrative of managed retreat from a resurgent desert.

Contrast this bickering with our wealth and technological might today, and contrast it again with the productive labor applied to solve this problem a century ago — when Portland cement, electrical grids, and diesel tractors had only just been invented, when most people in the United States still lived in poverty. California exists in its modern form because of our forefathers’ embodied will to fight back against Holocene desertification. Indeed, until the end of the last ice age about ten thousand years ago, much of the American West, under different climatic conditions, was a lush network of forests, lakes, and rugged mountains. 

In many ways, most of them positive, the world has moved on since the 1930s. We better understand the environmental trade-offs of the Hoover Dam: disruption of river ecosystems, the shrinking of the Colorado River Delta to less than 10% of its original size. Even if major rivers remained untapped, we wouldn’t necessarily want to divert them. But developments in technology could mean we don’t have to. What the West lacks in water it makes up for with an abundance of sunlight. Modern technology gives us the ability to inexpensively convert that constant stream of energy, which otherwise merely scorches the earth, into more water than 10 Colorado rivers could provide. With it, we can restore as much of the West to the water abundance the region hasn’t known since the ice age. 

It is easy to speculate about such grand visions in the abstract, so here I’m going to discuss one specific area. The specific project, which I first outlined on X, can transform Southern California and its relation to water, energy, and industry. This transformation will prepare the state and its neighbors for another miracle century of growth and wealth creation.

Just a couple of hours’ drive east of Los Angeles lie the Coachella and Imperial valleys, home to Palm Springs, some of the most productive agricultural land on Earth, and the Salton Sea, a large brackish lake that formed in 1905. Together with Los Angeles, this area uses over five million acre-feet (MAF) of water from the Colorado River every year, a river whose flow continues to trend downward due to the changing climate.

Today, several canals bring water for irrigation from the lower Colorado into the US side of the Imperial Valley, which extends southwards another 50 miles into Mexico. By (somewhat contentious) treaty, the last 1.5 MAF of the Colorado continues into Mexico, which also has vibrant agricultural activity in the Colorado delta area near Mexicali. The agricultural areas are, broadly speaking, low lying and historically were cyclically flooded — the bed of ancient lakes. The modern Salton Sea formed between 1905 and 1907, when an irrigation mishap diverted the Colorado into the Salton Sink, a geological depression formed by the San Andreas Fault. 

This natural sink has hosted lakes before, as the Colorado River sometimes diverted inland. Its most recent incarnation, Lake Cahuilla, which once covered 2,200 square miles, was recorded by some of the earliest European explorers but dried up some time in the 1700s. Today, the Salton Sea’s surface level continues to decline as evaporation exceeds inflows. Its salinity rises as it concentrates and is now too high to support any fish, causing several great die-offs in the early 2010s. 

The variable level also causes infrastructure challenges for communities that live around the lake and which first suffered major flooding in the 1950s. More recently, the shore has receded as the lake has shrunk, beaching boats and docks. Most troublingly, the agricultural runoff that maintains the sea is contaminated with salts, pesticides, and many metals that become airborne as the sea evaporates, leading to severe and widespread respiratory problems from the dust in the exposed lake bed. The air quality in the region is among the worst in the nation.

In short, the Salton Sea is a blight, a festering environmental catastrophe, and a source of enduring shame for California, a state that prides itself on environmental sensibility, technology, wealth, and entrepreneurial spirit.

Cursed it may well remain, since — until recently — the cost of desalinating the lake by itself was prohibitive, and there are no convenient sources of water in its catchment through which to regulate its surface level.

This has now changed. Solar photovoltaic (PV) panels are, acre for acre, 100 times more economically productive than farming is. A relatively small desert area adjacent to the fields, once developed for solar, will deliver enough insanely cheap electricity that it can transform the economy of the entire region. 

Desalination is the process by which salt is removed from water, turning brackish or seawater into drinkable fresh water. Modern desalination via reverse osmosis filtration is quite energy efficient, at just 1.8 kilowatt-hours/cubic meter. 

Why are solar PV panels so cheap? Solar panels are essentially large sheets of glass containing a thin layer of silicon configured so that light will push electrons through in one direction, generating electricity with no emissions, no fuel, no noise, no dust, and no moving parts. Built in factories refined continually for the last 50 years, solar panels have followed a similar cost curve to Moore’s Law for computers: ever greater volumes at ever lower prices — and no end in sight. Last year, the world installed about 437 GW of solar electricity, or roughly one acre of panels every 10 seconds. Earlier this year, panels fell to a record low of just $0.12/watt, and that record is certain to fall before long. In just the last decade, solar has fallen in price by a factor of 10. No other energy source has ever gotten that cheap that fast — and all indications are that both deployment and cost declines are accelerating. 

Fresh water production is just one of dozens of industries being upended by cheap solar, but the general rule applies. If it’s possible to use lots of cheap energy to make something, then sooner or later solar will be cheap enough to bring that product to a particular market at scale. For water in the US Southwest, that time is now. Solar can deliver power for about $0.02/kilowatt-hour (kWh), batteries for 24-hour utilization increase this to $0.12/kWh, meaning that the 1.8 kWh required for each cubic meter of water costs only $0.20 — and this is falling about 15% per year.

We must build a solar-powered environmental restoration machine that alleviates intense ecological pressures and guarantees water abundance for the Southwest forever by using reverse osmosis desalination to support the natural flow of the Colorado River. 

The cost of desalinated water is roughly half power ($0.20/cubic meter, as explained above) and half amortization of the physical desalination plant ($0.15-0.30/cubic meter). What makes the plant so expensive? There are a few different ways to do desalination, but the dominant modern technology is reverse osmosis (RO) — already deployed to the tune of more than 10 million acre feet (MAF) per year, primarily in the Middle East. ¹ RO uses a pressure gradient to force water through an extremely fine filter, concentrating brine on the pressurized side while a fraction of the input leaks through as water so fresh that often minerals need to be added back in for taste.

The pressure required is substantial, but the use of an improbable piece of mechanical equipment called a pressure exchanger allows the outgoing brine stream to pass its pressure to the incoming salt water, allowing RO to approach the thermodynamic efficiency limit required to yank all the salt ions out of fresh water. 

RO equipment is following its own, less dramatic decosting curve (learning rate currently around 10%), but it is fundamentally more complex than solar. Larger RO plants typically cost around $3,000/cubic meter-day, or $40/watt, which is comparable to a data center. This doesn’t preclude the possibility of major cost improvements, particularly if it can be customized for solar electricity and production cycles.

Despite relatively high capital costs, seawater RO (SWRO) routinely produces fresh water at $0.40/cubic meter, or $480/acre-foot. About half that cost is energy, so we can expect continued steep cost improvements for SWRO in the future. Less than $100/acre-foot should be achievable within 10 years. 

This application is not hypothetical. The Taweelah RO plant in Abu Dhabi, completed in 2022, produces 250,000 acre-feet of fresh water per year. A plant this size could, by itself, restore the Salton Sea in just a few years, though the full system would need to be somewhat larger to make a meaningful impact on agricultural fresh water supply. 

Solar PV and RO desalination are mature products with existing markets and supply chains. Unlike the previous century’s pioneering irrigation projects, this sort of development requires no new technology, merely the scaled application of existing processes and products at a level that would barely affect existing supply chains.

This is how it works.

A solar-powered RO desalination plant is built in the desert west of Yuma, convenient to existing irrigation canals and the Colorado River. It is fed by a large seawater pipeline that runs down the floodplain across the border to the Gulf of California, and also by a separate spur line that draws from the Salton Sea and runs parallel to the Coachella Canal. 

RO desalination splits the incoming ~3% salinity stream into two halves, one fresh and one ~6% salinity. This concentrated brine is fed to adjacent brine processing facilities (ideally in both countries) that exploit the region’s abundant solar and geothermal energy to extract potentially millions of tonnes of lithium, sodium, magnesium, chloride, and other metals found in seawater. The resulting depleted brine is piped back to the ocean where it is thoroughly diluted with raw seawater and discharged.

The fresh water is distributed into the region’s irrigation canals, enabling regulation of the Salton Sea’s level as well as its salinity. This would also preserve more of the Colorado’s natural flow into Mexico. The Coachella Canal passes within a few miles of the Colorado River Aqueduct, so this desalination system could potentially also feed fresh water into the Los Angeles municipal supply.

The project has multiple sources of revenue: water sales, brine products, and land value appreciation when the Salton Sea once again becomes compatible with human habitation. Indeed, were the lake level tamed and fresh water restored to support a diverse ecosystem, I think it would become comparable to Lake Tahoe in aesthetics, but with a much stronger industrial base due to abundant energy, water, and minerals.

It seems hard to believe that such a tiny corner of such a huge desert, so far from any roads that its existence would be unknown to all but a handful of airline passengers, could be capable of producing 5 MAF of fresh water per year — California’s entire Colorado River allocation! This is the power of solar energy. 

Importing seawater from Mexico would require cross-border coordination, similar to what Arizona and Mexico are already developing further down the Gulf. Mexican dependence on flows from the Colorado previously caused tensions in the 1970s, when US water use left Mexico with unusably salty water for its allocation, and again in the early 2000s, when the All-American Canal was resealed, cutting off about 67,000 acre-feet per year that crossed the border. 

Deeper development of agricultural resources in Mexico can never occur without more water, so a new solar desalination effort is an opportunity to use technology to create abundance where diplomacy has failed to deliver. Minimal Mexican involvement would entail approval for the construction of a pair of canals to bring water to and from the Gulf, but ideally the project would also include Mexican development of solar power, desalination, brine recovery, and related industries, further developing Mexico’s growing industrial power and increasing trade with the United States. 

Geographically, the region between Brawley and the Gulf is a flat, low-lying flood plain, which rises to a maximum altitude of about 30 feet above sea level at the saddle adjacent to the Cerro Prieto geothermal power plant, necessitating minimal pumping to move water to and from desalination. The canal could be covered in an extended solar array, providing power and reducing evaporation. 

This project to provide abundant water to the Imperial Valley, Salton Sea, and Mexico is, by historical standards, diplomatically uncomplicated, a low technical challenge, and of moderate scope. But do the economics stand up?

Let’s take a closer look at a block diagram showing how value would accrue across the proposed system.

The solar panels convert wasted sunlight into electricity, one of the most useful forms of energy, at the lowest cost ever in human history. The batteries make this power available at night, enabling production of water 24 hours a day. The RO desalination plant uses this power to strip salt out of fresh water, a remarkably efficient and high-maturity technology already deployed to the tune of more than 30 MAF/year. At $600/AF, this unit alone accrues $3 billion in annual revenue. 

At current prices, existing solar, battery, and desalination products installed at scale could cost around $33 billion, or roughly 10 times annual revenue counting water sales alone. The addition of a $10 billion brine recovery facility can substantially improve the project’s return on investment.

The brine plant is uniquely able to exploit higher concentrations of ocean salt ions, cheap geothermal heat and electricity, and California’s burgeoning demand for critical minerals. Five MAF/year of 6% salinity brine contains more than 10 million tonnes of magnesium, comparable to current global production, not to mention other light metals. The brine plant can also recover agricultural chemicals from the Salton Sea, including nitrates and phosphates. While nitrates are plentiful thanks to the Haber-Bosch process, phosphates are increasingly scarce. At light metal spot prices around $5000/T, a mature brine-extraction industry could net >$50b/year, which could help to keep the water cheap and food plentiful.

Finally, the “waste” product is nothing more than concentrated seawater, something anyone can make in their kitchen with a glass of water and a teaspoon of sea salt. Much has been made of the supposed perils of brine disposal, given that concentrated seawater is toxic. Ordinary seawater is also toxic, as anyone who has tried to drink a glass of it can attest to. The process of desalination, of removing some fresh water from the ocean, concentrates no more salt than the natural process of evaporation through which we get rain and snow — and by which the Gulf of California already has relatively high salinity. The key to safe disposal is rapid dilution through mixing at the brine return area. The diagram above assumes a 10:1 dilution, though that is definitely overkill.

Given the deep financial and human cost of the Salton Sea’s neglect and the decline of Californian agriculture, it seems surprising that this hasn’t already been done. And yet, just 10 years ago solar was so expensive that this sort of project was unthinkable. We need to recast the legacy of a century’s failed projects as challenges we can easily crush with the power of the sun. With cheap solar, the age of water scarcity will persist only as long as we let it.

The Imperial Valley is hardly unique in this respect. This demonstration of ecologically rational environmental stabilization, enabled by dirt-cheap solar energy, can become the model for climate-positive, wealth-positive humanistic development in other parts of the country and the rest of the world. Dozens of enormous river-fed agricultural areas are under threat, sparking dire predictions of water wars and starvation.

Instead, relatively modest investments of capital and land can backstop natural river flows, relieve pressure on ecosystems, and provide a foundation for climate resilience even as the next century most certainly has unpleasant surprises in store for us. 

Imperial County is, by California standards, relatively poor and undeveloped. Large-scale development of solar desalination can redirect excess sunlight to create water, critical minerals, and ecological stability for the Salton Sea. As outlined above, the development can pay for itself — it doesn’t require enormous federal or state investment. It requires only a decision to act in the interests of the people who already live there. Without visionary environmental engineering of this kind, the Salton Sea will fester forever as productive farmland faces desertification — a large and valuable part of the state permitted to wither for no good reason. With it, Imperial County can finally leverage its underutilized natural resources to enjoy the sort of growth and wealth much of the rest of the state takes for granted, at the same time as securing our economy and access to strategic minerals.

California should unabashedly leverage its mature industrial sector and visionary environmentalism to quell the growing water scarcity catastrophe, mend fences with Mexico, develop local industry, bolster agricultural production, restore the Salton Sea, build new shining cities along its shores, and flaunt its unequaled excellence by exporting alfalfa to all corners of the globe.