Among the fish populations that could be harmed by the Xayaburi dam in Laos is the critically endangered Mekong giant catfish, considered by the Guinness Book of World Records to be the world’s largest freshwater fish. The fish, which grows to 650 pounds and about 10 feet long, is only found in the Mekong River. It is migratory, moving between downstream habitats in Cambodia upstream to northern Thailand and Laos each year to spawn. Some experts fear the Xayaburi dam could block the migration and drive the giant catfish to extinction. (Photo by Courtesy of Zeb Hogan/University of Nevada, Reno)

A general view shows the Krasnoyarsk hydro-electric power station on the Yenisei River near the Siberian city of Krasnoyarsk, Russia, January 13, 2016. The power plant, owned by EuroSibEnergo company, part of En+ Group, with a generating capacity of 6,000 megawatt (MW), has a ferro-concrete dam 124-metres high and 1065-metres long and is the second largest Russian hydroelectric power station. About 85% of the energy generated is intended for the Rusal Krasnoyarsk aluminium smelter, according to representatives of the power station. (Photo by Ilya Naymushin/Reuters)

A girl uses a mattress as a raft during the flood after the Xepian-Xe Nam Noy hydropower dam collapsed in Attapeu province, Laos July 26, 2018. At least 26 people were killed and over 3,000 people stranded after a hydroelectric dam built collapsed in southeastern Laos, destroying thousands of homes and leaving an unknown number of dead. (Photo by Soe Zeya Tun/Reuters)

Children hold signs thanking truck drivers hauling rocks to the Lake Oroville Dam after an evacuation was ordered for communities downstream from the dam in Oroville, California, U.S. February 13, 2017. (Photo by Jim Urquhart/Reuters)

“Rivers Forgotten” is a journey through the passages and portals of the underground waterways that lie unseen below cities. Self-taught photographer Jeremy Kai brings these forgotten landscapes to light. Photo: Beneath the Toronto area, 2011. (Photo by Jeremy Kai)

Children stand in a boat at the banks of the polluted Yamuna River during a dust haze as they wait to give a ride to worshippers in New Delhi during World Environment Day June 5, 2010. (Photo by Reinhard Krause/Reuters)

Tourist Michel Watson found this pink dolphin making a splash in Brazil. The unusual creature, which hides deep in the Rio Negro river, was spotted leaping out of the Amazonian water brandishing its bizarre bright bubblegum color. Weighing in at nearly 300 pounds, the curious animal, known as an Amazon Pink River Dolphin, looked unusually agile as it rose above the waves. (Photo by Michel Watson)