You don’t need to be an architect, engineer or builder to be fascinated by large dams: indeed, these enormous structures seem to defy the laws of physics. And some countries certainly have large numbers of big dams, built over time to store water and generate electrical energy, as well as to control flooding. One country that definitely features among those with the most dams is the USA: partly due to its abundance of land and its many rivers, a great many dams have been built on watercourses here. In fact hydroelectric power currently represents 6.3% of all US electricity, as well as 31.5% of total renewable electricity in the country. This is mainly due to the largest American dams: let’s find out which they are.
The largest American dams: the criteria
How should we define the largest American dams? There are basically two main criteria: you can focus on the tallest dams in the USA, or you can look at which dams have the largest reservoirs, that is, which retain the largest quantities of water. The two criteria both yield equally interesting results, and it is not necessarily the case that the tallest dams have the largest capacity. So let’s take a look at both these rankings to find out which are the 10 largest American dams: the 5 tallest and the 5 with the largest capacity.
The tallest American dams
The USA has many very tall dams, each with a range of functions. Here they are.
1- Oroville Dam, 235 metres high
At a height of 235 metres, the Oroville dam is the tallest dam in the United States. Built on the river Feather, east of the Californian city of Oroville, it has 3 purposes: storing water, producing hydroelectric power, and controlling floods. Built between 1961 and 1968, it became the centre of attention in 2017, when two cracks – one on the main spillway and the other on the emergency spillway – led to the evacuation of 200,000 people. We should point out that the dam was subsequently repaired in record time, and returned to full and safe operation 2 years later, in 2019.
2- Hoover Dam, 221 metres
One of the most important engineering works of the last century was the Hoover dam, at 380 metres long, 220 metres high and 200 metres wide. It is located in the Black Canyon, along the Colorado River between Arizona and Nevada. Built between 1931 and 1936, the dam was innovative in many different ways, thanks to the use of technology that had never been tested before. The dam is currently used to produce electrical energy, and is visited by a million people every year. It is an absolutely enormous work of engineering that is said to contain enough concrete to pave a road running between San Francisco and New York.
3- Dworshak Dam, 220 metres
The Dworshak Dam, located in Idaho on the river Clearwater, is only a little lower than the Hoover dam. It is the third tallest US dam and the tallest straight-axis concrete dam in the western hemisphere. It was built between 1966 and 1973, and is used for water storage and the production of electrical energy. It is just over a kilometre long.
4- Glen Canyon Dam, 220 metres
The fourth largest dam in the United States in terms of height is also on the Colorado River, like the Hoover dam. This dam is in northern Arizona, however, near the town of Page. Built between 1956 and 1966 to create the Powell Lake, the construction of the Glen Canyon Dam had been planned and then postponed since 1924, partly because precedence was given to the Hoover Dam.
5- New Bullards Bar Dam, 197 metres
The fifth tallest dam in the United States is the New Bullards Bar Dam, an arch dam built during the 1960s and opened in 1969 in California, on the North Yuba River, not far from the town of Dobbins. The dam is used for irrigation, storing drinking water and producing hydroelectric power.
The largest US dams by capacity
Having see the largest American dams by height, let’s turn now to the 5 largest US dams according to reservoir capacity: as we will see, two of them also appear in the previous rankings.
1- Hoover Dam, 8.95 cubic miles
The second tallest dam in the USA is also the largest in terms of reservoir capacity. This enormous concrete structure, which creates Mead Lake, manages to hold an enormous 8.95 cubic miles of water: it’s a huge amount, although not as much as the world leader, the Kariba dam, which holds 44 cubic miles (equivalent to 185 cubic kilometres) and thus has no rivals to fear in this respect.
2- Glen Canyon Dam, 8.53 cubic miles
The fourth tallest dam in the United States is also the second largest American dam in terms of reservoir capacity. This dam forms Powell Lake, as we mentioned above, with 8.53 cubic miles of water, retained by a dam that is 480 metres long.
3- Garrison Dam, 7.05 cubic miles
The third largest American dam by reservoir capacity is the Garrison Dam, on the Missouri river in North Dakota. Built between 1947 and 1953, this dam is 64 metres tall and an amazing 3.5 kilometres long, creating Lake Sakakawea.
4- Oahe Dam, South Dakota, 6.98 cubic miles
Moving from North Dakota to South Dakota, we find the Oahe dam, also on the Missouri river; it is also extremely long, at 2.8 kilometres, with a height of 75 metres, and it forms a reservoir that can hold 6.98 cubic miles of water, that is, Lake Oahe. It was built between 1948 and 1962.
5- Fort Peck Dam, 5.52 cubic miles
Concluding the top 5 largest American dams by reservoir capacity is the Fort Peck dam, again on the Missouri river. Stretching for an incredible length of 6.5 kilometres and with a height of 76 metres, it was built between 1933 and 1940.
