built on the cliff, 2nd tallest in the world

As the name suggests, rock dams are barrier dams made of soil, rock or local mixed materials, very different from concrete dome dams and gravity dams. The pouring volume of a concrete dam is less than a few million tons, for a giant dam like the Three Gorges Dam, the volume of concrete poured is even more than 70 million tons. The cost of each ton of concrete is more than 100 yuan (VND 360,000), so the cost of concrete alone has reached hundreds of millions of yuan. If in a delta area or a place with convenient road traffic, this concrete price is still acceptable; but the Mesopotamia hydroelectric station is located on high mountains and deep valleys, transportation is extremely inconvenient, and that will cause the price of concrete to increase sharply. In addition, when traffic is hindered by bad weather, roads are difficult to supply in time, which will seriously affect the project progress. So the builders had to use local materials and used the most common local gravel for construction.