The 5GW Grand Ethiopian Renaissance Dam (GERD), which is 145 meters high, is set to double electricity generation in Ethiopia. In September 2023, the fourth and final phase of filling a reservoir for the electric power plant on the Blue Nile was completed, prompting renewed outcry from Egypt, which has long opposed the $4 billion (€3.7 billion) megaproject.

Egypt and Sudan are worried about the impact of GERD, thanks to which Ethiopia will have more control over water it depends on to keep Nile Delta farmland flourishing. The idea is that water should keep flowing but Ethiopia's neighbors aren't convinced by its assurances that it will not use the dam to divert water for irrigation, particularly as climate change makes water scarcer.

Since the 1990s, China has built 11 giant dams on the Mekong, making it the world’s biggest producer of hydropower, which is its second biggest source of electricity after coal. With Laos, Thailand, Vietnam and Cambodia also all dependent on the river, the construction of the dams has caused consternation downstream.

Downriver, the Mekong Delta has suffered as China's dams have changed the timing and flow of the water. Droughts have become more frequent and fish stocks have suffered, with fishing and farming communities in Thailand and Cambodia hit particularly hard. Satellite data has shown above-average snowmelt and rainfall, adding to Chinese stretches of the river.

The Souapiti dam in Guinea. China has invested in hundreds of hydropower projects in Guinea and other African countries and across the world, from Laos to Portugal, Kazakhstan to Argentina, In the past, such colossal infrastructure projects were often financed by the World Bank, but China is rapidly taking over a major funder and doesn't seek agreement from countries sharing the same river basins.

The Souapiti dam in Guinea, financed by the China International Water and Electric Corporation, will provide 450MW in a country where only a minority of citizens have access to a reliable electricity supply. But to create its giant reservoir, 253 square km of land will be flooded and in anticipation some 16,000 people from over 100 villages have been displaced, according to Human Rights Watch.

The construction of the Itaipu dam on the Parana between Brazil and Paraguay flooded huge swathes of forest and one of the world's most impressive waterfalls, displacing 65,000. It has also caused tensions between the two countries: Though they signed an agreement to work together on the jointly-owned project in 1973, the fact that the bulk of the power goes to Brazil has been controversial.

The Mexico-US border conjures up images of mgrants, and Donald Trump's dream of building a wall to divide the two countries. As well as tensions over people heading north, there have been worries over the Colorado River’s flow in the opposite direction. By the time the river reaches Mexico, it has passed through seven US states and numerous dams that divert its waters to irrigate US crops.

The US and Mexico have been working together to use the Morelos Dam on their shared border to water the Mexicali Valley, with a "pulse" system that mimics the river's natural flow into the Colorado Delta. Water politics expert Scott Moore says this shows "cooperation between the US and Mexico, but also between environmental groups, farmers, irrigation districts and ecological management."