At 145 meters high and almost two kilometers long, the Grand Renaissance Dam is expected to become Ethiopia's biggest source of electricity. As Africa's largest hydroelectric power dam, it will produce more than 15,000 gigawatt-hours of electricity, beginning in 2022. It will source water from Africa's longest river, the Blue Nile.

With more than 50% of Ethiopians still living without electricity, the government wants the dam to be up and running as soon as possible, so tens of millions of residents will be able to access power. The first of a total of 13 turbines are due to be operational by mid-2021.

Construction on the current dam began in 2011 — but the site was identified between 1956 and 1964. The coup of 1974 meant the project failed to progress, and it was not until 2009 that plans for the dam were resurrected. The $4.6 billion (€4.1 billion) project has consistently been the source of serious regional controversy, with its plan to source water from the Blue Nile.

In a few years, this entire area will be covered in water. The reservoir which is needed to generate electricity is expected to hold 74 billion cubic meters of water. Ethiopia wants to fill the artificial lake as soon as possible, but neighboring countries are concerned about the impact this might have on their own water supplies.

Egypt, in particular, fears that filling the reservoir too quickly will threaten their water supply and allow Ethiopia to control the flow of the Blue Nile. Ethiopia is insisting on having the reservoir filled in seven years. Ethiopian Prime Minister Abiy Ahmed met with Egyptian President Abdel-Fattah al-Sisi on Sunday, to discuss the matter.

However, two days of negotiations between Ethiopia, Egypt, and Sudan in Washington over the weekend failed to solve the reservoir issue, despite the US stepping in to mediate. With no progress over the last four years, Prime Minister Abiy Ahmed even called on South Africa's President Cyril Ramaphosa — and the 2020 chairperson of the African Union — to intervene in the dispute.

Amidst the heated negotiations, up to 6,000 employees are still working around the clock to get the dam completed by the deadline. The working conditions are not for the faint-hearted: In the hottest months, temperatures on the construction site can reach up to 50 degrees.

Over the years, construction was also delayed significantly due to ongoing corruption and mismanagement issues. Last month, 50 people were charged with severe graft offenses relating to the dam, including the former CEO of Ethiopian Electric Power (EEP).

The Munduruku people live mainly in forest regions and riverbanks, in villages spread along the Tapajos River in the Brazilian states of Para, Amazonas and Mato Grosso. With an estimated population of 12,000 to 15,000 people, the Munduruku are the most numerous indigenous group along the free-flowing Tapajos River.

The dwellers of the Sawre Muybu Indigenous Land have sought for at least three centuries to officially demarcate their territory. The 178,000-hectare area includes rainforest that is threatened by illegal loggers and mining — and more recently, by the construction of reservoirs for hydropower.

Munduruku people live largely as they have for centuries. Villages are represented by women known as "cacicas." Maria Aniceia Akay Munduruku, from the upper Tapajos, has taken part in her people's movement against the construction of hydropower dams, including by demarcating indigenous land. She doesn't speak Portuguese: Her husband helps her to communicate with others outside the village.

The Tapajos River is the essence of life for the indigenous Munduruku people. They depend on its water for sustenance, and to get around. The waters teem with vitality — there are 324 identified species of fish living in the waters, beside Amazonian manatees and giant otters.

Along the river also live hundreds of species of birds, lizards and amphibians. Tapirs and giant anteaters ply the riverbanks, while jaguars and ocelot also prowl the rainforest and savannah. The region is among the world's most important for rare land and water species.

Munduruku children attend the village school, under the guidance of indigenous teachers. In this picture, girls play in the shared classroom at Sawre Muybu village during their holiday break. Animals such as monkeys, parrots, dogs and capybaras are welcome among the children.

Manioc flour is the staple food in Munduruku villages — cassava planted on the family farm is crushed, shredded and then roasted in a wood-burning stove. Also sweet potatoes, yams and bananas are grown. Although Munduruku consume mainly food grown in the local fields, items such as sugar, salt and coffee have also made their way into the traditional diet. They are purchased in town once a month.

An aerial view shows the Teles Pires dam, on the homonymous tributary to the Tapajos. The lighter green color indicates the area of forest that was submerged — critics point out that rotting vegetation from inundated forest produces considerable quantities of methane, a powerful greenhouse gas. The specter of ongoing drought also casts doubt on future usability of such hydropower stations.

This aerial image shows construction at the Sao Manoel hydropower dam, which is supposed to begin operation by January 2018. Partially funded by Chinese companies, the cost of the project is estimated to reach €600 million euros. The plant, located on the Teles Pires River, will have the capacity to generate 700 megawatts of electricity.

If built, the Sao Luiz do Tapajos dam would inundate this stretch of the river — including its shallows, rapids, beaches, waterfalls, inlets and shores. Once full, it would create a reservoir the size of New York City. Planned dams could flood up to 7 percent of indigenous territory, resulting in loss of land, poorer water quality and less fish — deeply affecting Mundukuru livelihood.

For the structure on the right, a German company last week received the German Innovation Award for Climate and Environment. It is a fish elevator, which transports fish from the lower to the upper water level - and vice versa - of a weir. This elevator enables fish to cross the man-made obstacle and continue their journey along the river.

The fish elevator, constructed by the German company Baumann Hydrotec, runs mainly on water power. Fish enter a container inside a water-filled chamber at the bottom of the weir. Eventually a latch closes. Water enters the chamber and lifts the container up. The latch opens, and the fish continue their journey.

But why do fish need an elevator at all? The reason is that they migrate up and down rivers. Salmon are famous for their long journey. They travel hundreds of kilometers from the sea up the rivers to reach spawning grounds, where they lay their eggs. Freshwater eels also travel a long way to reproduce. And a lot of other fish species migrate just to search for food.

Migration ends as soon as something like this shows up: a dam. Without help, fish are unable to reach the upper level. And they might not survive being washed down with the rushing water from the upper to the lower level.

Conservationists might come up with a solution like gathering fish on one level of a dam and transporting them to the other level - by monorail. This is what actually happens at the Hwacheon Dam in South Korea. The dam interrupted an important fish migration route when it was built in 1944.

Fish ladders are more natural. They offer an alternative route from the upper to the lower level and vice versa, allowing fish to overcome the man-made obstacle themselves. Though manmade, fish ladders don't have to be elaborate, expensive constructions - they can be small and simple, like this one.

When the weir, dam or lock is economically important and quite big, the fish ladder will look very impressive. This one in Geesthacht near Hamburg, Germany, on the river Elbe, is 550 meters (1,800 feet) long. It is the biggest fish ladder in Europe, consisting of 45 interconnected pools that the fish have to pass through.

Fish ladders can take the form of spiral staircases. Fish work their way up from one pool to the other. This construction, though, needs less space than the usual kind of fish ladder. An added benefit: the roundish pools prevent the fish from hurting themselves in the course of their journey.

One of these spiral staircases for fish is to be found at a hydropower station near Kiel in northern Germany. Looking like some futuristic industrialstructure, it is 200 meters (656 feet) long, consists of 36 pools and covers an incline of 3 percent.

Eels are weak swimmers, they just slither up- and downstream. They need special eel ladders: watery, ascending ramps with brush-like structures on the ground. Special rest areas allow them to have a break during their climb. Eels' ladders are often built alongside ordinary fish ladders.