Yves here. Yours truly has been under-reporting in Links the number and severity of bad climate change effect stories, since if I did merely a pretty good job, they would eat up all of Links. On top of record heat stories from every reasonably populated continent (including record daily minimum), flooding, droughts, and knock-ons (poor harvests, increased pathogen and pest levels), one regular category is cities running short of water. Cape Town was an early victim but it now has plenty of company.
This story discusses first-level responses, which is rationing and harvesting rainwater. But what comes next? For instance, in California, which has been subject to droughts, the main line of attack has been household use, when agriculture greatly exceeds that, and a lot of that is profligately wasteful like growing rice. So even these initial responses are hamstrung by political interests.
By Tanya Petach, the Climate Science Fellow at the Aspen Global Change Institute and Kaitlin Sullivan, a freelance journalist who covers health, science, and the environment. Produced in partnership with Energy Innovation and the Aspen Global Change Institute. Originally published at Yale Climate Connections, their content-sharing partner
In April 2024, more than 9 million residents of Bogotá, Colombia’s capital city, were told to collect rainwater – if the city was lucky enough to experience a storm.
Fed by the Guatiquía River, the Chingaza reservoir system, which supplies the area with 70% of its water, had reached critically low levels.
To make what was left stretch through a dry spell with no clear end in sight, authorities divided the city into nine zones. Every day, one of the zones would go dry for 24 hours. No toilet would flush. No glass of water would be filled from the tap. Dishes would have to go unwashed.
Bogotá Mayor Carlos Galan told residents they should be prepared to live with the water restrictions for a year.
“The call is to take care of every drop of water,” the mayor’s office said, according to CBS News.
A month later, 2,000 miles away in Mexico, the Cutzamala system of reservoirs reached historic lows. The water reserves supply a substantial portion of water to Mexico City’s 22 million residents, who faced mandatory rationing.
Bogotá and Mexico City’s stories mirror those of cities across the globe. The amount of water stored in lakes worldwide has drastically and steadily decreased since 1992, according to a 2023 study published in the prestigious research journal Science. During those 30 years, freshwater lakes collectively lost an average of 600 cubic kilometers of water storage annually – 17 times the volume of Lake Mead, the largest reservoir in the United States.
A Global Crisis
The cause is a combination of human-caused overuse and unprecedented shifts in the climate, the researchers found.
Increasing temperatures, accelerated evaporation, and unpredictable shifts in rain and snow patterns and the runoff these events create have made urban water sources increasingly unstable.
These factors, coupled with unsustainable water consumption, are responsible for about half the water losses over the last 30 years. They’ve pushed cities around the globe closer to Day Zero, when water supply would be depleted and taps would run dry.
But understanding which of these stressors is having the biggest impact on each water system is the cornerstone for creating solutions.
The Cautionary Tale of the Aral Sea
In living memory, the Aral Sea, which straddles the Uzbekistan-Kazakhstan border, was the fourth-largest lake in the world.
Engineers diverted massive amounts of water from the Aral Sea starting in the early 1960s to irrigate one of the world’s largest cotton farming operations. The lake rapidly shrank over the next three decades.
That decision made the Aral Sea a poster child for what happens when humans overuse water in arid regions.
The Aral Sea as captured by satellite images in 2000 and 2018. (Image credit: NASA Earth Observatory)
Today, the lake covers one-tenth of the surface area that it did in 1920. Five and a half million hectares of the lake – an area the size of Lake Michigan – is dry. If rusting fishing boats didn’t stud the taupe-colored desert, there would be little reason to believe the surrounding area is a lake bed.
A similar story is unfolding for dozens of critical waterways, from the Maipo River in Chile, the basin of which provides 80% of Santiago’s water, to the Colorado River in the United States, which supplies water to 40 million people. Both rivers have been overpromised and overused by sprawling cities and agricultural operations.
How Does Climate Change Affect Water Supplies?
Even the best-laid plans can be thwarted by the uncertainties climate change brings. Fueled largely by hotter temperatures, evaporation is a significant threat to drinking water supplies worldwide.
Evaporation in reservoirs and natural lakes increased by nearly 60% between 1985 to 2018 – more than scientists previously thought, according to a study published in Nature Communications in 2022.
In central Argentina, a salt lake called Laguna Mar Chiquita, or “Lake Little Sea,” shows how increased pressures from climate change interact with overconsumption. Lack of rainfall and high temperatures have meant the three rivers that feed Lake Mar Chiquita deliver less water. Without rainfall to irrigate their crops, farmers divert more water than usual from the lake so their plants won’t die. Evaporation, exacerbated by heat, adds pressure to the lake. In the summer of 2022 and 2023, Argentina set a record with 10 heat waves.
The Colorado River, which supplies water to seven Western states, nearly 30 Native American tribes, and two states in Mexico, faces similar threats. The river irrigates 15% of American agriculture, including around 90% of vegetables grown in winter. The American West is a quarter century into a megadrought that hasn’t been remedied by two consecutively wet winters.
As a result, more water is being used than is coming in.
The U.S. Department of the Interior monitors Lake Mead, which is fed by the Colorado River. If experts expect reservoir levels to dip below a certain point, the federal agency releases less water, leaving downstream shareholders across two countries with less water. In 2022, this happened for the first time.
Arizona, Nevada, and Mexico have all faced cuts to their shares of the Colorado River in recent years, a trend expected to continue in 2024.
“A warmer atmosphere is a thirstier atmosphere, and without a compensating increase in precipitation, which has not occurred, humans and ecosystems will be left with less water,” hydroclimatologist Park Williams of the University of California, Los Angeles, told the Los Angeles Times.
What Can Cities Do About Dwindling Water Supplies?
There have already been a series of small, continued efforts that have been able to stave off Day Zeros.
Cutting water use is the most obvious line of defense. It’s a scenario people around the world watched play out during a narrowly averted crisis in Cape Town, South Africa, in 2018. Starting in 2015, dwindling reservoir storage for Cape Town’s water supply brought the city perilously close to Day Zero. In response, city officials implemented harsh restrictions that cut water consumption by 50% of 2015 levels. Those efforts, coupled with the return of seasonal rains, kept the city’s water supply from running out.
Some nations have already implemented changes to their water infrastructure in an effort to reduce the amount lost to evaporation and overuse, such as Las Vegas’ nonfunctional turf ban.
In southern Brazil’s Passaúna reservoir, floating solar panels have the potential to be a win-win. The shimmery sheets reduced evaporation in the reservoir by 60%, while at the same time powering homes, businesses, and industry with renewable energy. Floating covers and shade balls can have the same evaporation-thwarting effect, especially for reservoirs in arid climates. Though these technologies show promise for decreasing evaporation, ongoing research is evaluating side effects, such as impaired water quality.
“Understanding the primary stressors on lake water losses is often a prerequisite for management solutions,” said Fangfang Yao, a postdoctoral fellow at the Cooperative Institute for Research in Environmental Sciences who led the Science study, told Yale Climate Connections.
And addressing climate change is a necessary part of the solution, too. “Reducing greenhouse gas emissions nationally and internationally will help alleviate further water losses due to evaporation,” Yao said.
Anyone know if floating solar panels are a recipe for metal/Cadmium/plastics tainted water?
Yes, and the answer is that only a tiny % of solar panels made world wide use cadmium.
And the cadmium is sealed into the panel by glass on both sides as all cad/tel panels I’m aware of use glass on glass design.
It’s an easy fix, just use normal silicon panels.
As to the back sheet on normal panels breaking down, I suppose, but I’ve never seen that.
And metal? I don’t know how aluminum would be an issue?
I’ve seen a fair amount of back sheet issues in cheap panels, and my research indicates it is common. Cracks appear in the plastic back sheet in between the silicon cells over time (5-10 years) and this allows moisture to reach the conductive components and cells “fail”. A thorough dry and application of an exterior grade paint sealer can “revive” these panels which is a method I have used successfully. As to how much contamination of water under a floating panel array would result, I can’t say, but plastic and UV equals breakdown.
I don’t know how aluminum would be an issue?
I remember to have read something about aluminium in contact with acidic liquids ending up producing some nasty aluminium-containing compounds and this being a reason to avoid wrapping, say, tomatoes or pineapple in aluminium foil. But the water pH would have to be unnaturally low.
Virtually none. There is plenty of research out there on both land and water arrays if you want to go into google scholar and use the appropriate search terms – a lot of it has been done in the Netherlands in particular. Modern panels are mostly silicon – while a variety of metals and other toxic materials can be used in making the panels, its not in a form that can leach into water, even in worst case scenarios. Some studies have found minor elevations of some metals in reservoirs arising from new sealants or treatments for the floats and other structures, but none have been found in dangerous levels. Panels themselves are made of largely inert or non-bioreactive materials, but often ancillary structures or sealants or post construction treatments are overlooked. Most reservoir managers are fully aware of the sources of potential pollution in reservoirs and are always on the lookout for issues – such as with leisure boat anti-fouling treatments.
Probably the most significant identified hazard from reservoir solar arrays are the potential for toxic algae to grow under the shade – UV is a powerful disinfectant. But this can apply under many other circumstances and its a purely theoretical threat. The use of solar panels for reducing evaporation in reservoirs has almost entirely benign or positive benefits – not least that reducing evaporation also reduces the potential for natural build up of metals or other toxins.
One of the other aspects that I’d like to add is that there are two major types of water storage: covered and uncovered. Much of what people think of as storage are the big uncovered reservoirs, which provide a number of benefits; however, there has been a move away from the for treated water as they are exposed to a number of potential pollutants which may necessitate additional treatment.
Covered storage systems would in theory be great locations for PV as they are flat, are not used for another purpose, and the areas need light maintenance (like monthly lawn mowing) already. Adding solar seems like a no-brainer. However, they are not as large as the uncovered reservoir for raw water, and the maintenance requirements might conflict with solar generation. I never considered them before, but it’s an interesting idea.
They are really going to have to start redesigning our cities. Years ago Sydney here in Oz went through a severe water shortage with the dam feeding it dropping precariously low. Fortunately the rains did come but then people started to ask why all the water falling in the Sydney basin was being routed by storm water drains out to the Pacific and wouldn’t it be better to store as much as possible for future shortages.
Of course this post reminded me of how about twenty years ago the water services of a South American nation were sold by the corrupt government to a French multinational until the people rebelled against this deal. What struck me at the time was how that deal was worded so for example if you collected rainwater off your roof which fed into your own storage tank, you did not own that water but that French corporation did – who would then proceed to charge you for that water. It was about this time that I was familiarizing myself with a new (for me) term – Neoliberalism.
Evaporation in reservoirs and natural lakes increased by nearly 60%
This alone is cause to declare an emergency! The laws of physics have been upended by those nasty humans!
Public water supplies depend on electric power to move water to households. How much public water delivers water pressure through gravity feed and water towers? What other means are used? If electric power were lost for a month through a failure in the electric Grid, what would happen? How would people in big city handle their sewage? Only one building tower kept their lights going in one of the last great power outages that affected New York City. [ https://www.pinterest.com/pin/444589794434613881/ ]
As climate disasters crowd the news, what news of plan ‘B’ to manage/adapt-to little snags in the flows of energy and of water and sewage?
The thought makes me gag, but it could easily come down to industrially recycled water for most uses. Except drinking, and many of us already choose to buy purified water these days. Also there could be a method for using depleted aquifers as a place to store water instead of open reservoirs.