Why don't people open up the north-south water system and alleviate the flood disaster in the south through the canal?

The spatial distribution of precipitation in China is uneven, with more in the south and less in the north. More in the east and less in the west. In addition, the rainfall in China is unevenly distributed in time, with more in summer and less in winter. It is precisely because of the uneven distribution of rainfall in China in geography and time that droughts or floods often occur.

The time distribution of rainfall is relatively easy to solve. As long as more reservoirs are built and the lake area is expanded, the orderly regulation of water resources can be realized. For example, release more water in the dry season and intercept flood peaks in the flood season. It can minimize the occurrence of drought and flood disasters.

Since the uneven distribution of rainfall in time can be solved, can the uneven distribution of rainfall in space be solved by building canals?

Beijing-Hangzhou Grand Canal and South-to-North Water Diversion If you have any impression of China's landform, you will know that China's landform is high in the west and low in the east, so rivers flow from west to east. However, due to the high terrain in the west and low terrain in the east, the natural rivers in China rarely flow from south to north, and the precipitation in the south is difficult to be used by the north.

In the past, the Sui Dynasty dug the Grand Canal connecting the north and the south. The Grand Canal starts from Yuhang, Hangzhou and ends in Beijing in the north.

The Beijing-Hangzhou Grand Canal not only diverted water from South to North, but also accelerated communication between North and South. In the past, people could only transport goods by land, but now they can transport goods by water, which strengthens the connection between north and south.

Besides the Beijing-Hangzhou Grand Canal, China has also been organizing construction in recent years? South-to-North Water Diversion Project? This project has greatly relieved the drought pressure in the north. At present, some drinking water in Beijing and Tianjin comes from the South-to-North Water Transfer Project.

Canal Since the Beijing-Hangzhou Grand Canal and the South-to-North Water Transfer Project can solve the partial spatial imbalance of rainfall in China, why not build more canals connecting the north and the south?

Actually, it's about money.

Although the most water-deficient area in China is the western region, the eastern region has a large population and a greater demand for water, so the construction of canals in the eastern region will be given priority.

However, the population density in the east is very high, so people around the canal need to be moved out to build the canal; Moreover, the construction of the canal will also flood the surrounding cultivated land and factories. And these industries need to be compensated accordingly, so the money needed to build the Grand Canal is very huge.

More importantly, China has built three South-to-North Water Diversion Projects, and these projects have also played a corresponding role, transporting a lot of water resources to the north, so there is no need to build new canals.

Flood disaster In fact, the flood disaster in the south can not be alleviated by transporting it to the north through the canal, but it may also cause flood disasters on both sides of the canal.

As we know, there is little difference in topography between the north and the south of China, so the river course is gentle and the water flow speed is slow. If there is a flood in the south, which leads to a flood disaster in the south, then the flood disaster in the south can not be transported to the north quickly because of the slow flow of the canal, but will accumulate in the canal area and cause a flood disaster.

In order to alleviate the flood disaster in the south, it is necessary to expand the area of local lakes, because lakes are natural reservoirs, and if there is a flood disaster in the local area, lakes can play a role in flood diversion.

In addition, large reservoirs can also be used as reservoirs, which can intercept flood peaks and reduce local economic losses by manually adjusting the water output of reservoirs.

Take the Three Gorges Dam as an example. Some time ago, the Yangtze River No.3 flood was formed. The inflow of the Three Gorges Reservoir reaches 50,000 cubic meters per second, while the outflow of the Three Gorges Dam is only 37,000 cubic meters per second. The rest of the water was stopped in the Three Gorges Dam and slowly discharged.

It can be said that if there are not many dams in the upper reaches of the Yangtze River to intercept floods and weaken flood peaks, the flood disaster in the middle and lower reaches of the Yangtze River will be more serious.

It is concluded that the construction of the North-South Canal can not share the flood disaster in the south, but it will cause greater flood disaster on both sides of the canal because of its flat terrain and slow flow rate.

Floods often occur in southern China. In order to control floods, China has long started to return farmland to lakes and build reservoirs and dams. Just because the local population is large and the middle and lower reaches of the Yangtze River are flat, floods are easy to rush out of the waterway, leading to flooding.