It should be pointed out that weight of the water in the Sanxia reservoir is very small compared to the mountains beside the rivers. First, the average density of rocks to form the mountains should be at least 2 times of the water. In this simple calculation, we assume that each of the mountains beside the river is in shape of upward triangle and they are in thousand meters above the original river bed. On the other hand, the water in the reservoir is at the maximum 175 meters above the sea level and forms or reverse triangle. Therefore, It has no reason to say that the reservoir caused the earthquakes. Taking a simple example, if the mountains beside a cross-section of the reservoir is 1000 m above the river bed and the average slope angle is 45 degrees considering the hard rock in Sanxia region, the water is at the maximum 145 m deep toward the lower portion of the reservoir. Take the average density of mountain rock to be 2 tons per cubic meter and water is 1 ton per cubic meter. If we take a slice of 1 meter thick cross-section of the mountain and the water, the total weight of the mountain above the river bed is about 4,000,000 tons while the water is about 21,025 tons. Comparing the two, the weight of the added water due to the construction of the Sanxia reservoir in this slice is only about 0.5% of that of mountain rock. The weight of the added water is very insignificant. If the ground is originally stable without frequent earthquake activities, there should be at least a safety factor of 2.0 or more. In other words, the earth crest located under the selected slice should be able to withstand at least 8,000,000 tons of mountain rock before causing significant deformations that might cause potential earthquake. Through such simple calculation, it can be shown that the construction of the reservoir in Sanxia might increase the earthquake susceptibility by a merely 0.25% to the maximum. Statisticians can tell us how remotely that possibility is. Therefore, do not follow those groundless accusations without using your head.
On other hand, I could agree that the construction of Sanxia reservoir can indeed cause some changes in local weather such as local flooding beside the river.
It also should be pointed that most of the US rivers have been dammed up either for waterway transportation, recreational use or hydropower generation purposes. There are only a few small free-flow rivers left in US now. The waterway transportation is cheapest means of transportation if the speed is not a critical factor. We should realize that China is significantly under-used its water resources. If large coal barges can be used to haul the coal and other mineral resources along the yellow river by dammed it up stage by stage from west to east parts of China, many of the problems such as crowded trains in holiday seasons, the unbalanced development between the east and west, etc. As a nation, China is short of water resources, great efforts should be made to better utilize them.
On other hand, I could agree that the construction of Sanxia reservoir can indeed cause some changes in local weather such as local flooding beside the river.
It also should be pointed that most of the US rivers have been dammed up either for waterway transportation, recreational use or hydropower generation purposes. There are only a few small free-flow rivers left in US now. The waterway transportation is cheapest means of transportation if the speed is not a critical factor. We should realize that China is significantly under-used its water resources. If large coal barges can be used to haul the coal and other mineral resources along the yellow river by dammed it up stage by stage from west to east parts of China, many of the problems such as crowded trains in holiday seasons, the unbalanced development between the east and west, etc. As a nation, China is short of water resources, great efforts should be made to better utilize them.
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