Dubai, UNITED ARAB EMIRATES — A global rush for the next wave of generative artificial intelligence is increasing public scrutiny on an often-overlooked but critically important environmental issue: Big Tech’s expanding water footprint.

Tech giants, including the likes of Microsoft and Alphabet-owned Google, have recently reported a substantial upswing in their water consumption and researchers say one of the main culprits is the race to capitalize on the next wave of AI.

Shaolei Ren, a researcher at the University of California, Riverside, published a study in April investigating the resources needed to run buzzy generative AI models, such as OpenAI’s ChatGPT.

Ren and his colleagues found that ChatGPT gulps 500 milliliters of water (roughly the amount of water in a standard 16-ounce bottle) for every 10 to 50 prompts, depending on when and where the AI model is deployed.

Hundreds of millions of monthly users all submitting questions on the popular chatbot quickly illustrates just how “thirsty” AI models can be.

The study’s authors warned that if the growing water footprint of AI models is not sufficiently addressed, the issue could become a major roadblock to the socially responsible and sustainable use of AI in the future.

ChatGPT creator OpenAI, part owned by Microsoft, did not respond to a request to comment on the study’s findings.

“In general, the public is getting more knowledgeable and aware of the water issue and if they learn that the Big Tech’s are taking away their water resources and they are not getting enough water, nobody will like it,” Ren told CNBC via videoconference.

“I think we are going to see more clashes over the water usage in the coming years as well, so this type of risk will have to be taken care of by the companies,” he added.

For Meta, its these warehouse-scale data centers that generate not only the highest percentage of its water use but also the lion’s share of its energy use and greenhouse gas emissions.

In July, protesters took to the streets of Uruguay’s capital to push back against Google’s plan to build a data center. The proposal sought to use vast quantities of water at a time when the South American country was suffering its worst drought in 74 years.

Google reportedly said at the time the project was still at an exploratory phase and stressed that sustainability remained at the heart of its mission.

In Microsoft’s latest environmental sustainability report, the U.S. tech company disclosed that its global water consumption rose by more than a third from 2021 to 2022, climbing to nearly 1.7 billion gallons.

It means that Microsoft’s annual water use would be enough to fill more than 2,500 Olympic-sized swimming pools.

For Google, meanwhile, total water consumption at its data centers and offices came in at 5.6 billion gallons in 2022, a 21% increase on the year before.

Both companies are working to reduce their water footprint and become “water positive” by the end of the decade, meaning that they aim to replenish more water than they use.

It’s notable, however, that their latest water consumption figures were disclosed before the launch of their own respective ChatGPT competitors. The computing power needed to run Microsoft’s Bing Chat and Google Bard could mean significantly higher levels of water use over the coming months.

“With AI, we’re seeing the classic problem with technology in that you have efficiency gains but then you have rebound effects with more energy and more resources being used,” said Somya Joshi, head of division: global agendas, climate and systems at the Stockholm Environment Institute.

“And when it comes to water, we’re seeing an exponential rise in water use just for supplying cooling to some of the machines that are needed, like heavy computation servers, and large-language models using larger and larger amounts of data,” Joshi told CNBC during the COP28 climate summit in the United Arab Emirates.

“So, on one hand, companies are promising to their customers more efficient models … but this comes with a hidden cost when it comes to energy, carbon and water,” she added.

U.S. Senator Ron Wyden warned that foreign governments are spying on smartphone users by compelling Apple and Google to turn over push notification records, according to a letter he sent to Attorney General Merrick Garland Wednesday.

Wyden, D-Ore., said his office investigated a tip from last year alleging that government agencies have been “demanding” these records from both companies. Since push notifications like news alerts, emails, and social media alerts travel through Apple and Google’s servers, they can reveal unique insights about how individual people use particular apps, Wyden explained in the letter.

Governments can force Apple and Google to hand over these records, just like they can be compelled to share any other information they have regarding their users, according to the letter. In the U.S., however, Wyden said information about push notification records cannot be released to the public.

“Apple and Google should be permitted to be transparent about the legal demands they receive, particularly from foreign governments, just as the companies regularly notify users about other types of government demands for data,” Wyden wrote. “I would ask that the DOJ repeal or modify any policies that impede this transparency.”

Push notification records can reveal which app received a notification, when it was received, the phone and Apple or Google account that the notification was delivered to, and in some cases, the unencrypted text displayed in the notification, according to the letter.

Wyden did not specify which governments have asked Apple and Google for push notification records. The senator’s office did not immediately respond to CNBC’s request for comment.

A source confirmed to Reuters that foreign government agencies, as well as U.S. government agencies, have asked both Google and Apple for information from push notifications. For instance, the agencies have asked for metadata that can help connect anonymous users on messaging apps to specific Apple and Google accounts, according to the report.

“In this case, the federal government prohibited us from sharing any information,” an Apple spokesperson said. “Now that this method has become public we are updating our transparency reporting to detail these kinds of requests.”

A Google spokesperson said the company shares Wyden’s commitment to keeping people informed about requests for push notification records.

“We were the first major company to publish a public transparency report sharing the number and types of government requests for user data we receive, including the requests referred to by Senator Wyden,” the spokesperson said in a statement. The company did not clarify where it publishes requests for information about push notification records, or if it is restricted.

The Department of Justice did not immediately respond to requests for comment.

TikTok parent ByteDance plans to spend up to $5 billion buying back stock, a person familiar with the matter told CNBC, as one of the world’s most valuable startups seeks to give shareholders a chance to cash out of their holdings.

ByteDance is offering shareholders $160 per share, which values the firm at around $268 billion, the person said.

There is no timeline for the completion of the share repurchases, but ByteDance has asked shareholders if they’d like to sign up to the program, the person said.

ByteDance declined to comment.

Buybacks by private companies are often a way for shareholders to make a return on their early investments, especially when there is no liquidity event like an initial public offering or acquisition.

The latest round of buybacks for shareholders comes just under a month after ByteDance offered to repurchase restricted stock units (RSU) or options from employees for the same price of $160 per share.

ByteDance, which was founded in 2012, has been tipped to go public for the last few years, but has faced an increasing number of headwinds.

The Chinese giant’s most popular overseas app TikTok has faced scrutiny from lawmakers across the world, in particular in the U.S., where critics have questioned the safety of American data on the platform.

ByteDance is also cutting hundreds of jobs from its gaming division, where the company has aggressively expanded without success.

The firm has been hit by a slowing Chinese economy and by stricter domestic regulation in the internet sector.