The Yangtze River is the largest river in China. During the period of 1998, a catastrophic flood disaster occurred in the Yangtze River basin in China. Under the strong leadership of the Party and the country, millions of soldiers and civilians fought bravely against floods and made another great victory in the history of China.

After this victory, we will learn from the bitter experience, and we will ask such a question: 1998 flood is another catastrophic flood disaster in this century after 1954. However, according to preliminary data, the flood volume of 1998 is much less than that of 1954, about 50 billion cubic meters less.

Schematic diagram of water regime in the main stream of the Yangtze River (unit: meter)

Analysis process 1:

1998 There are many reasons for the flood disaster, but the direct causes are abnormal climate and excessive rainfall. Since June, there have been three continuous large-scale rainfall processes in the Yangtze River Basin. In July, the flood volume of hydrological stations in the middle and lower reaches of the Yangtze River exceeded 1954, of which Yichang Station121500 million cubic meters exceeded 65,438+. Hankou station164.8 billion cubic meters, more than 195412 billion cubic meters. The Yangtze River flood mainly occurs in Jianghan Plain in the middle reaches. Here, the terrain is low, the river course is curved, and the flood discharge is not smooth, and it is also the place where many streams of incoming water meet. If the tributaries flood at the same time, they will meet here. It will inevitably lead to a catastrophic flood disaster in the Yangtze River. The most important thing is that part of the flood storage is much less than 1954. The data show that the flood volume in 1998 is about195 billion cubic meters, while the safe flood storage volume in 1954 is about 40 billion cubic meters, and the total flood storage volume in 1998 is about 65,438.

Comparison of Two Extraordinary Floods in Yangtze River Basin 1954 and 1998

Project name 1954 1998

Precipitation (mm; June10 ~ August 24, the average value of the whole Yangtze River basin) 674 577

Average flow (m3/s) Yichang 66800 63600

Luoshan 79900 68600

Hankou 76 100 72300

Water volume (subject to the maximum flood volume of 30 days, unit: 100 million cubic meters) Yichang 1380 1330.

Hankou 1730 1739

Average water level in Shashi (m) 44.67 45.22

Luoshan 33. 17 34.95

Jiujiang 22.08 23.03

Hankou 29.73 29.43

At this time, people will ask: is the elevation of the Yangtze River water level due to the increase of siltation in the Yangtze River bed?

Analysis process 2:

① About riverbed siltation.

In order to develop hydropower resources, cascade hydropower stations and small reservoirs have been built in the middle and upper reaches of many major rivers in China, which has greatly weakened the functions of rivers and lakes as natural ecosystems, resulting in limited natural water surface of rivers and lakes, intensified river siltation and competing improvement of riverbed dams. According to the long-term observation data, the main channel of the Yangtze River is basically stable, but due to some factors, some sections of the Yangtze River have changed in erosion and deposition, the most obvious being the Honghu section below Jingjiang River, which is greatly influenced by Jingjiang River.

② About lake siltation.

In recent decades, Tongjiang Lake has lost about 6.5438+0.2 million hectares due to blind reclamation. Only the original 22 large Tongjiang lakes in the Yangtze River lost 57.6 billion cubic meters of volume due to unreasonable reclamation and development. Under the same flow rate, the reduction of lake volume leads to the increase of water level. In this case, the flood level in flood season is generally about 654.38+00 meters higher than the domestic ground, resulting in danger. It's hard to prevent. For example, since 1949, the capacity of Dongting Lake has been reduced by more than 4 billion cubic meters due to siltation, and the capacity has been reduced by nearly 1600 cubic meters due to reclamation. The siltation of Poyang Lake is very small, but it is reduced by more than 8 billion cubic meters due to reclamation 1400 square kilometers. The area of Hubei province has decreased by 5700 square kilometers. Since 1.949, the cultivated land in Hunan, Hubei, Jiangxi, Jiangsu and Anhui provinces has increased by about 1.400 square kilometers due to reclamation.

Analysis process 3:

According to statistics, the average annual erosion amount of ground solid matter in the upper reaches of the Yangtze River is 65.438+0.568 million tons, and the average annual sediment transport amount at Yichang Station in the main stream of the Yangtze River is 530 million tons, and the sediment transport ratio is below 0.33. The average annual sediment transport capacity of Yichang Station is 430 million tons, and that of Datong Station downstream is 468 million tons. The main difference between Yichang and Hankou is that they are deposited in caves. Most of it flows into the East China Sea. According to research, forest vegetation not only has high economic value, but also has irreplaceable ecological and social benefits. The interception rate of forest to rainfall is as high as 65,438+02.6%, which can reduce surface water loss by 85.65,438+0% and soil erosion by 58% compared with no forest land. Obviously, the destruction of vegetation will inevitably aggravate soil erosion and river sediment. Runoff decreases. Soil erosion also leads to siltation of rivers, lakes and reservoirs, raising river beds, reducing reservoir capacity and shrinking lakes. However, over the years, the ratio of forest cutting and regeneration has been 1 1: 1. According to 1957 survey, the forest coverage rate in the Yangtze River basin is 22%, and the soil erosion area is 363,800 square kilometers. Accounting for 20.2% of the total basin area. By 1986, the forest coverage rate has been reduced by half, and the area of soil erosion has doubled to 739,400 square kilometers, accounting for 4 1% of the whole basin area.

(The above data comes from news materials and extracurricular materials at that time. )

Conclusion:

First of all, the ecological damage is serious, especially the forest ecosystem in the upper reaches of the Yangtze River has been seriously damaged for a long time, which has caused retaliation from nature. The concentrated expression is that under the situation of rapid population growth, over-utilization of land resources and unreasonable development and logging have cut off some rivers and dried up springs, causing floods in rainy season.

Secondly, the area of lakes in the middle and lower reaches of the Yangtze River has been greatly reduced because of blind lake enclosure, among which blind lake enclosure and occupation of floodplain are the main reasons for the rise of flood level in the Yangtze River.

Third, the negative ecological impact of unreasonable water conservancy construction on rivers can not be ignored. A large number of water conservancy projects have destroyed the natural ecological function of rivers and may aggravate the harm of floods.

Suggestions and hopes:

1998 The Yangtze River flood caused serious losses and people paid a huge price. On the one hand, it is caused by abnormal climate and concentrated rainfall, but on the other hand, we should fully face up to the problems such as serious ecological damage, siltation of rivers and lakes, reclamation around lakes and weak water conservancy facilities, which can not but arouse people's reflection.

(1) It is urgent to protect the ecology. Ecological destruction is one of the chief culprits of the flood crisis. The fundamental measures to alleviate the flood crisis are afforestation, wetland protection and soil erosion control.

(2) On the other hand, we should emphasize the full use of land resources. On the one hand, we should vigorously strengthen land use management, and try our best to save land and rationally develop and utilize land resources in industrial, transportation, building and residential construction. On the basis of giving full play to the production potential of existing cultivated land and preventing soil erosion, we will actively and steadily develop and utilize various land resources such as wasteland and coastal beaches, and prohibit indiscriminate reclamation of lakes and occupation of floodplains.

(3) In the western development, protect the natural environment and ecological balance, comprehensively manage the whole Yangtze River basin according to the actual situation, coordinate the relationship between man and nature, improve the quality of land environment, and realize the sustainable development of the Yangtze River basin.

I hope we can better manage the Yangtze River!