The energy produced to power a single lamp in Northumberland, England in 1878 was the first hydroelectric project in the world. Within a decade, hundreds of plants were in operation around the globe. The appeal of hydroelectric power is straightforward. It provides clean, reliable, and almost free electricity. The power generated by hydroelectric plants can also be stored, making it more flexible than any other renewable sources. However, as this type of energy expands at an ever-increasing scale, its externalities are becoming more and more evident. This is the Ilisu Dam on the Tigris River in Turkey. The project is part of Turkey’s centennial vision and is a prestige showpiece for the government. It is expected to generate as much energy as a nuclear power plant, enough to power 1.3M homes and contribute an estimated $250M/year to Turkey’s economy. However, as a consequence of the rising water level upstream, caused by the construction of the dam, multiple river settlements will soon be submerged. One of those is the ancient town of Hasankeyf. It is thought to be one of the oldest continuously inhabited settlements on Earth, dating as far back as 10,000 BC, containing thousands of caves, temples, and tombs. Thus, in addition to displacing almost 80,000 people, the dam will also be responsible for the destruction of a unique piece of cultural heritage. Hydro plants can pose an even more immediate danger to a population located downstream. More than 100 million people depend on the Mekong River in Southeast Asia for their livelihoods. However, there has recently been a rush to dam the river. This is particularly visible in Laos, where the government has the ambition of turning the country into “the battery of Asia” by building close to 100 new dams. In the summer of 2018, following heavy rainfall, one of the dams in the construction in the Attapeu province collapsed disastrously causing an immediate flash flooding through the nearby villages. It is reported that as a result, 48 people have died, at least 98 are still missing, and around 7,000 were displaced. The construction of a dam is, in effect, geoengineering, and it inevitably leads to some adverse consequences to the local environment. The Chinese Three Gorges “Super” Dam on the Yangtze River is the world’s largest hydro plant in terms of capacity. According to NASA estimates, when filled, the gorge would hold 10 trillion gallons of water. To put this in perspective, a shift of mass of that magnitude would have an effect on Earth’s rotation, and increase the length of a day by 0.6mis. Needless to say, a dam of that size can have a severe impact on the natural flow of water, leading to significant changes in the river’s hydrology, and infrastructure. In addition, the dam has also been linked to an increased frequency of earthquakes and landslides in the area. Another example of how hydro plants can have a negative effect on nature could be seen in Brazil’s Belo Monte dam. In case you want to know more, please click on the link in the description. Often times, hydro plants can also have a geopolitical impact. If a state upstream builds a dam, it will inevitably affect other nations downstream. An example of such a conflict is the Grand Ethiopian Renaissance Dam. Once operational, it is expected to alleviate Ethiopia’s energy crisis, where less than half of the population has access to electricity. The countries downstream, however, are less enthusiastic, and claimed that they will be negatively affected due to the lesser flow of the river to the territory. As a result, this project has directly contributed to an escalation of tensions between Ethiopia and Egypt, with the former claiming that Egypt is seeking to prevent the country from economic development, and the latter claiming that it threatens the livelihood of 100M of its citizens. On one hand, Ethiopia is a sovereign state with full control of its land, water, and other resources; but on the other, it is easy to understand Egypt’s concerns. It is, after all, a dry desert state, and depends on the River Nile for most of its water. Taking away that water resource is perceived as an existential threat, especially taking into account that Egypt is already under the internationally-recognized water poverty threshold. Hydroelectric power is unique. It offers a clean energy alternative with a high economic potential, especially in areas with low natural resources. Despite that, policymakers shouldn’t ignore the potential negative impacts as oftentimes these unforeseen costs can outweigh the benefits.