Growing cities, overuse of fertilizers and factory wastewater have degraded China's water supplies to the extent that half the nation's rivers and lakes are severely polluted. China aims to spend $850 billion to improve filthy water supplies over the next decade, but even such huge outlays may do little to reverse damage caused by decades of pollution and overuse in Beijing's push for rapid economic growth. Photo: Fishermen row a boat in the algae-filled Chaohu Lake in Hefei, Anhui province, June 19, 2009. (Photo by Jianan Yu/Reuters)

The US Navy Blue Angels numbers 5 and 6 fly below Sean Tucker (above) as he pilots the Oracle Challenger III over San Francisco, California as part of a practice run for Fleet Week on October 6, 2016. (Photo by Josh Edelson/AFP Photo)

The AMECA robot from the manufacturer Engineered Arts is in the Deutsches Museum Nuremberg (Future Museum), Bavaria on May 3, 2022. AMECA is a humanoid robot that will be presented to the general public for the first time in Europe as part of the Blue Night on May 7, 2022 in Nuremberg. (Photo by Daniel Karmann/dpa/Alamy Live News)

New York Islanders left wing Pierre Engvall and Columbus Blue Jackets Sean Kuraly (7) fight in the third period at UBS Arena on January 20, 2025 in Elmont, New York. (Photo by Wendell Cruz/USA TODAY Sports via Reuters)

Lake Baikal is the world's oldest lake, at 25 million years (possibly older), and deepest, averaging 744.4 metres (2,442 ft).

Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the world, containing roughly 20% of the world's unfrozen surface fresh water.

A female brown bear with cubs fishing on Lake Kronotskoye as part of the South Kamchatka, Russia on Sanctuary, August 13, 2017. (Photo by TASS/Barcroft Images)

A boat is stranded on Poyang Lake in Lushan City, China during low-water season on November 3, 2016. (Photo by Xinhua/Barcroft Images)

Taliban security forces ride horses along the Qargha Lake on the outskirts of Kabul on May 11, 2023. (Photo by Wakil Kohsar/AFP Photo)