Hi, I’m Yves. We don’t report much on the number and severity of bad news about the effects of climate change on Links, because even if I wrote a pretty good article, it would take up all of the space on Links. In addition to record heatwaves (including record coldest daily temperatures), floods, droughts and their effects (reduced crop yields, increased disease and pests) on a reasonably populated continent, urban water shortages are a regular feature. Cape Town was an early victim, but now has many friends.
This article discusses the first step: channeling and collecting rainwater. But what about beyond? In drought-stricken California, for example, the main response is domestic use, but agriculture far exceeds it, and much of it is wasted. Like rice farmingSo even these initial responses are being stymied by political interests.
Article by Tanya Petachi, research climate scientist at the Aspen Global Change Institute, and Caitlin Sullivan, a freelance journalist covering health, science, and the environment. Produced in partnership with Energy Innovation and the Aspen Global Change Institute. Yale University ClimateContent Sharing Partners
In April 2024, more than 9 million residents of Bogotá, the capital of Colombia, I was asked to collect rainwater. – If the city is lucky enough to be hit by the storm.
Water levels in the Chingaza Reservoir, the source of the Guatiquia River and which provides 70 percent of the region’s water, had reached critically low levels.
To survive the seemingly endless drought, authorities have divided the city into nine districts. Every day, one of the districts goes without water for 24 hours. You can’t flush your toilets. You can’t fill a glass from the tap. You have to wash your dishes.
Bogota’s mayor, Carlos Galan, told residents to prepare to endure water restrictions for a year.
“We are being asked to pay careful attention to every drop of water,” the mayor’s office said. CBS News.
A month later, 2,000 miles away, Mexico’s Catzamala Reservoir System Lowest in historyThe reservoir provides a significant amount of water to Mexico City’s 22 million residents, who face mandatory rationing.
The situation in Bogotá and Mexico City mirrors that of cities around the world: The amount of water stored in lakes around the world has declined dramatically and steadily since 1992, according to a 2023 study. study The research, published in the prestigious journal Science, found that over the past 30 years, freshwater lakes have lost an average of 600 cubic kilometers of water per year. 17 times the volume of Lake Meadthe largest reservoir in the United States.
Global crisis
The researchers concluded that a combination of human overexploitation and unprecedented climate change was to blame.
Rising temperatures, accelerated evaporation, unpredictable changes in rain and snow patterns, and the runoff these phenomena create, are making the city’s water sources increasingly precarious.
These factors, combined with unsustainable water consumption, account for roughly half of water losses over the past 30 years. They are driving cities around the world closer to “day zero,” the point at which water supplies run dry and there is no water left in the taps.
However, understanding which of these stressors have the greatest impact on each aquatic system is the basis for developing solutions.
Lessons from the Aral Sea
For as long as people can remember, the Aral Sea, which straddles the border between Uzbekistan and Kazakhstan, 4th largest lake In the world.
Engineers began draining large amounts of water from the Aral Sea in the 1960s. Early 1960s It was built to irrigate one of the world’s largest cotton growing facilities, and over the next 30 years the lake shrank rapidly.
This decision made the Aral Sea a textbook example of what happens when humans overuse water in arid regions.
Satellite images of the Aral Sea in 2000 and 2018. (Images courtesy of NASA Earth Observatory)
Today, the lake’s surface area is one-tenth of what it was in 1920. 5.5 million hectares of the lake (an area the same as Lake Michigan) are dry, and if it weren’t for the rusting fishing boats dotting the brown desert, there would be little reason to believe the surrounding area is a lakebed.
Similar situations are occurring at dozens of other important waterways. Maipo River in ChileThe basin supplies 80% of Santiago’s water. Colorado River in Americaprovides water to 40 million people. Both rivers are expected to be overused by urban expansion and agricultural activities.
How will climate change affect water supplies?
Even the best-laid plans can be hampered by the uncertainties that climate change brings. Evaporation, caused primarily by rising temperatures, poses a major threat to drinking water supplies around the world.
Between 1985 and 2018, evaporation from reservoirs and natural lakes increased by about 60%, more than scientists previously thought. study Published in Nature Communications in 2022.
In central Argentina, Laguna Mar ChiquitaMar Chiquita (aka the “Little Sea Lake”) shows how growing pressures from climate change interact with overconsumption. Lack of rainfall and rising temperatures are reducing the amount of water in the three rivers that feed Mar Chiquita. With no rainfall to irrigate crops, farmers are diverting more water than usual from the lake to keep plants from dying. Evaporation is exacerbated by heat, putting pressure on the lake. In the summers of 2022 and 2023, Argentina broke records. 10. Heat Wave.
The Colorado River is Supplies The river, which supplies water to seven western states, about 30 Native American tribes and two Mexican states, faces similar threats. The river irrigates 15 percent of U.S. agriculture, including about 90 percent of winter vegetable crops. 25 years since the megadrought began that Not improved We had two consecutive wet winters.
As a result, More water is being used than what’s coming in.
The U.S. Department of the Interior monitors Lake Mead, which receives water from the Colorado River. If experts predict the reservoir’s water level will fall below a certain level, the federal agency will reduce water releases, reducing the amount of water downstream shareholders across the two countries receive. This happened for the first time in 2022.
Arizona, Nevada, and Mexico All Facets The Colorado River’s share has increased in recent years, and this trend is expected to continue. 2024.
“As the atmosphere warms, water gets thirstier, and unless that’s compensated for by increased precipitation that hasn’t happened before, people and ecosystems will have less water,” Park Williams, a hydroclimatologist at the University of California, Los Angeles, told the Los Angeles Times.
What can cities do about their dwindling water supplies?
There has already been a series of smaller, ongoing efforts that have been able to thwart zero-days.
Reducing water use is the most obvious line of defense. It’s a scenario the world watched as a crisis was narrowly averted in Cape Town, South Africa, in 2018. Starting in 2015, dwindling reservoirs for Cape Town’s water supply brought the city dangerously close to Day Zero. In response, city officials implemented strict regulations, reducing water consumption to 50% of 2015 levels. These efforts, combined with a return of seasonal rains, saved the city’s water supply from drying up.
Some countries have already implemented changes to their water infrastructure to reduce water losses through evaporation and overuse. Las Vegas bans on non-functioning lawns.
In the Passauna Reservoir in southern Brazil, Floating Solar Panels It could be a win-win. Reduce reservoir evaporation by 60%At the same time, we will power homes, businesses and industries with renewable energy. Floating Cover and Shade ball These techniques have a similar evaporation-inhibiting effect, especially in reservoirs in arid climates. These techniques are expected to reduce evaporation, but ongoing research is evaluating their side effects, such as water quality degradation.
“Understanding the primary stressors of lake water loss is often a prerequisite for management solutions,” Fanfan Yao, a postdoctoral researcher at the Cooperative Institute for Environmental Sciences who led the Science study, told Yale Climate Connections.
Tackling climate change is also an essential part of the solution: “Reducing greenhouse gas emissions at home and abroad can help mitigate further water loss through evaporation,” Yao said.
