[Edit May 2024: This concept was republished in Asterisk Magazine.]
Just a couple of hours drive east of Los Angeles lies the Imperial Valley, home to Palm Springs, some of the most productive agriculture on Earth, and the Salton Sea. 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.
For many years, California’s approach to the problem has been to seek comfort from its senior water rights and its outsized power compared to neighboring states, while telling stories of managed decline and fallowing farms in both the Imperial and Central Valleys. Few remember the enormous public works projects that built the dams on the Lower Colorado a century ago and brought water hundreds of miles across the desert, making life possible for the tens of millions of people who now call it home. These projects were visionary and we stand here today because of their embodied will to fight back against Holocene desertification.
The advent of cheap solar gives us another powerful tool to fight against the desert and to bring life and water to huge swaths of the western US, starting with the Imperial Valley. In an earlier post I wrote more generally about supporting rivers. Here, I will discuss the outline of a specific project that can transform Southern California and its relation to water, energy, and industry to be ready for another miracle century of growth and wealth creation.
Today, several canals bring water from the Lower Colorado into the US part of the Imperial Valley for irrigation. By 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 frequently flooded. The modern Salton Sea formed in 1905 when an irrigation mishap diverted the Colorado into the sink, itself formed by crustal extension and rifting. Its previous incarnation Lake Cahuilla dried up around 1700.
The Salton Sea’s level continues to drop due to evaporation, leading to increasing salinity (now too high to support any fish, causing several great die-offs in the early 2010s) and infrastructure challenges for communities that live around the lake, in addition to severe and widespread respiratory problems from dust from the exposed lake bed. 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, wealth, and entrepreneurial spirit.
Well may it remain, since the cost of desalinating the lake by itself is prohibitive and there are no convenient sources of water in its catchment by which to regulate its level.
This has now changed. Solar photovoltaic panels are, acre for acre, 100 times more economically productive than farming. A relatively small desert area adjacent to fields, once developed for solar, can deliver enough insanely cheap electricity that it can transform the economy of the entire region.
In short, we need to build a reverse osmosis desalination plant that backs up the natural flow of the Colorado. A solar powered environmental restoration machine that alleviates intense ecological pressures and guarantees water abundance for the southwest forever.
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 PV-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 sea water pipeline that runs down the flood plain 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 desal 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 sea water. The resulting depleted brine is piped back to the ocean where it is thoroughly mixed with sea water 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 desalination, and the preservation of more of the Colorado’s flow into Mexico. The Coachella Canal passes within a mile 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 once the Salton Sea once again becomes compatible with human habitation. Indeed, were the lake level tamed and restored to support a diverse ecosystem, the excesses of agricultural exploitation remediated, I think it would become comparable to Lake Tahoe in aesthetics, but with a much stronger basis of industry due to abundant energy, water, and minerals.
This map shows the area of solar panels required to feed the RO and brine plants. 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! The adjacent agricultural areas grow plants that require water, planting, harvesting, fertilizers, pesticides, and the right kinds of weather, all to capture the sun’s energy in the form of digestible leaves, nuts, and fruits – at 0.01% the energy throughput efficiency of solar.
Let’s take a closer look at a block diagram showing how value accrues in the 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 100% utilization of the higher capex systems downstream. The RO desal 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, primarily in the Middle East. At $1000/AF, this unit alone accrues $5b in annual revenue.
The brine plant is uniquely able to exploit higher concentrations of ocean ions, cheap heat and electricity, and California’s burgeoning demand for critical minerals. 5 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. At spot prices around $5000/T, a mature brine extraction industry could net >$50b/year, which can help to keep the water cheap and food plentiful. 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.
Finally, the “waste” product is nothing more than concentrated sea water, something anyone can make in their kitchen and which turbulent mixing with the ocean can effectively dilute, nullifying impact at the intake and return.
Ten years ago, solar was too expensive to make this possible. That is no longer the case. The world deployed about 450 GW of solar in 2023, and for the first time energy cost no longer dominates the cost of desalinated water. In other words, we are now in the age of water abundance.
California should unabashedly exploit its mature industrial sector and visionary environmentalism to quell the growing water scarcity catastrophe, mend fences with Mexico, build 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.