1, upstream area:
(1) development task: hydropower resources development.
The reasons for the rich hydropower resources in the Three Gorges are analyzed from the aspects of climate, topography and water system characteristics.
Climate: The basin above Wuxia belongs to subtropical monsoon climate and alpine climate, with abundant precipitation and snowmelt water.
Topography: The Three Gorges is located at the junction of the second and third steps of China's topography, with a large gap.
Water system: There are many tributaries in the upper reaches of the Yangtze River with a long history and a huge water system.
(a) the Yangtze River Three Gorges and the Yangtze River Three Gorges area
1, Three Gorges of the Yangtze River
Refers to the Yangtze River from Chongqing Fengjie Baidicheng to Hubei Yichang Nanjinguan 193 km reach. It is the collective name of Qutang Gorge, Wuxia Gorge and Xiling Gorge.
The Three Gorges is one of the largest canyons in the world.
2. Three Gorges region of Yangtze River
Refers to the flooded area of Yichang-Chongqing section of the Three Gorges Project and its surrounding areas. It is roughly bounded by the flooded area of the Three Gorges Project and its surrounding resettlement scope, including more than 20 counties (urban areas) along the coast of Chongqing from Yichang, Hubei Province to the backwater of the Three Gorges Reservoir Area.
The Three Gorges area of the Yangtze River and Hengduan Mountain area are rich in hydropower resources. Why is the largest hydropower development project in the Yangtze River currently located in the Three Gorges area of the Yangtze River, rather than the relatively sparsely populated Hengduan mountainous area?
Natural factors: The two areas are rich in hydropower resources, located in mountainous areas and narrow river valleys, which are suitable for dam construction. However, the geological structure in Hengduan mountain area is more complicated, and the crustal activity is more frequent, while the geology in the canyon area is relatively stable. The dam-building conditions in the Three Gorges area are better than those in Hengduan mountain area.
Socio-economic factors: (1) The construction conditions of hydropower stations are different: The Three Gorges area is backed by the southwest hinterland of China, facing the economically developed middle and lower reaches of the Yangtze River, located in the southwest and central parts of China, at the junction of the western and central economic zones, and in the heart of Chinese mainland, with good socio-economic conditions and traffic conditions. Hengduan mountain area is located in the economically backward southwest of China. The socio-economic conditions and traffic conditions of dam construction are poor. (2) The power market is different: the power market of hydropower stations in the Three Gorges area is vast and far-reaching, and the power market in Hengduan Mountain area lags behind that in the southwest. (3) The comprehensive benefits of hydropower stations are different: the benefits of hydropower stations in Hengduan Mountain area are single, while those in Three Gorges area are huge.
(B) Comprehensive benefits of the Three Gorges Project
1, Positive and Negative Effects of Three Gorges Project Construction
Comprehensive Effects of Three Gorges Project
(1) flood control benefits of the Three Gorges Project
The Primary Goal of Three Gorges Project Construction: Flood Control
(2) Power generation benefits of the Three Gorges Project
The Three Gorges Hydropower Station on the Yangtze River is the largest hydropower station under construction in the world (Yitaipu Hydropower Station is currently the largest hydropower station under construction in the world).
What positive role does the construction of the Three Gorges hydropower play in improving the environmental quality of the eastern coastal cities in China?
Reduce the consumption of coal, oil and other mineral energy in eastern cities, thereby reducing the emission of harmful gases such as carbon dioxide and sulfur dioxide, avoiding pollution hazards such as acid rain and reducing waste residue emissions.
(3) Shipping benefits of the Three Gorges Project
Shipping from Yibin, Chuanjiang to Chongqing runs through mountains and valleys, with large drop, rapid current, many dangerous beaches and low navigation capacity. After the completion of the Three Gorges Project, the water level in the reach rose, the rapids were submerged, the water flow slowed down, the waterway deepened and widened, and 10,000-ton ships could reach Chongqing directly from Shanghai. Therefore, after the completion of the Three Gorges Reservoir, the shipping conditions in the upper reaches of the Chuanjiang River have been fundamentally improved.
1, the traffic location of the Three Gorges: guarding the upper reaches of the Yangtze River, it is an important channel connecting Central China and East China in Southwest China; The Liujiao Line runs through this area, which is an important place to connect the north and the south. There are important river ports. It is also the intersection of expressways and an important distribution center for goods.
2. The cause of the Three Gorges of the Yangtze River: the earth's crust rises and the river water cuts.
3. Reasons for the site selection of the Three Gorges Project: From the hydrological point of view, the site selection is located at the exit of the Three Gorges, with large water volume and rapid water flow; Geologically, this area is composed of granite, and the earthquake intensity is relatively small. From the engineering point of view, the river is narrow and convenient for construction.
4. The Three Gorges Project is the largest project in the world, with the largest submerged area, the most difficult resettlement and the greatest benefit.
5. At present, the hot issues of Three Gorges construction are ecology, cultural relics protection, sediment deposition, investment and financing.
Favorable area of interest action process
The Three Gorges Flood Control Reservoir has the functions of regulating flood peak and storing and discharging floods in the middle and lower reaches.
Upon completion, the Three Gorges Hydropower Station will be the largest power station in the world, which will alleviate the energy shortage in the central and eastern transmission areas of China.
Shipping the Three Gorges Reservoir can deepen and widen the upstream channel, slow down the water flow, improve the shipping conditions of the Yangtze River and promote the circulation of materials between the east and the west.
supply water
The construction of aquaculture Three Gorges Project will have a great impact on water supply and agricultural irrigation in the middle and lower reaches of the city, water transfer in the middle route of South-to-North Water Transfer Project and aquaculture in the middle and lower reaches of the reservoir area.
Reservoir area, etc
Scenic spots along the way include Baidicheng, Twelve Peaks in Wushan, Sanyou Cave and Zhaojun's hometown.
(2) Ecological environment construction:
Causes of ecological and environmental problems and harmful measures
Collapse, landslide and debris flow have complex terrain and large slope, which destroys the upstream ecological environment; Lead to sediment deposition in the middle and lower reaches of the Yangtze River, raise the riverbed, increase the threat of floods, and strengthen the construction of Yangtze River shelter forests and water conservation forests; Implement the protection policy of closing hillsides to facilitate afforestation, irrigating and planting grass, and implement protective management and development of existing forests.
Natural disasters of soil erosion
Man's destruction of vegetation
Background knowledge: Collapse, landslide and debris flow.
Collapse: refers to a natural geological phenomenon that large rock mass on steep slope suddenly collapses under the action of gravity. It can be caused by strong physical differentiation of fractured rock mass, rainwater infiltration or earthquake. Large-scale collapse is called "landslide", which often destroys buildings and blocks rivers or traffic routes.
Landslide: refers to a natural geological phenomenon that the rock mass or soil mass on an unstable slope slides down along a certain sliding surface (or sliding zone) under the action of gravity. The action of surface water and groundwater and unreasonable engineering activities destroy the stability of rock mass and soil on the slope, which are often the main reasons for landslides.
Debris flow: refers to a sudden flood filled with a lot of sediment and stones, which is mainly found in mountainous plateau areas. Where the terrain is steep and there are loose debris deposits on the surface, it is easy to form when it encounters heavy rain or a large amount of melted ice water flows out. When it broke out, the mountains shook, water, sand and stones gathered and rolled down the steep slope. It lasts for a short time, but it is fierce, often flooding farmland, blocking rivers and destroying subgrade bridges and culverts and other buildings.
(1) Impact of Three Gorges Project;
Positive influence (favorable influence) and negative influence (unfavorable influence)
The occurrence area is mainly in the middle and lower reaches, mainly in the reservoir area.
The concrete effects are as follows: ① Effectively reduce the damage of flood to the ecological environment in the middle and lower reaches, improve the living environment; ② Conducive to the prevention and treatment of schistosomiasis in the middle and lower reaches; ③ Reduce the atrophy and siltation of Dongting Lake; ④ Increase the flow in the middle and lower reaches in dry season, improve the water quality in dry season; ⑤ Adjust the local climate; ⑤ Reduce the harm of environmental pollution and acid rain. ① Flooding land and cultivated land by reservoir impoundment may cause new soil erosion and environmental pollution, and may induce earthquakes. Increase the possibility of geological disasters such as landslides; ④ Affect the natural landscape of the Three Gorges; (5) affecting the living environment of aquatic organisms and rare species; ⑤ The sediment deposition in the reservoir area and the reservoir tail is intensified; (5) breed mosquitoes and affect health.
The Causes of Ecological Environment Problems and the Harmful Countermeasures
Irreversible eco-environmental problems are irreversible, but measures can still be taken to remedy or restore some lost eco-environmental problems, such as flooding farmland reservoirs, rising water levels, less farmland under the submerged line, aggravating the contradiction between population and less land, rationally developing existing land resources, developing large-scale agriculture, and solving the shortage of cultivated land.
The flooded cultural relics reservoir stores water and the water level rises. The flooded cultural relics are damaged, and the flooded cultural relics are relocated and protected.
It affects the barrier function of the Three Gorges Dam, the migration and spawning routes of Chinese sturgeon, the habitat environment of baiji and the rare species and biodiversity.
Reversible ecological and environmental problems with great influence, such as soil erosion, reservoir area, contradiction between man and land, improper development of rural migrants, and urban relocation, aggravate siltation in the middle and lower reaches of reservoirs and lakes; Destroy the ecological environment in the reservoir area ① Adjust the agricultural structure, develop large-scale agricultural production ② Transform low-and medium-yield sloping fields and "three-run fields", develop high-standard terraced fields ③ Give preferential policies and funds, and strengthen ecological environment management and soil and water conservation.
The flow conditions of reservoirs with sediment problems have changed greatly after impoundment, which leads to sediment deposition in the reservoir area and the backwater area at the tail of the reservoir and affects the service life of the reservoir. Threatening the navigation of Chongqing Port (that is, obstructing navigation) ① The reservoir operation mode of "storing clear water and discharging muddy water" is adopted, so that the incoming sediment tends to be generally balanced; (2) port regulation and waterway dredging.
The problem of reservoir-induced earthquake has little influence, so effective measures can be taken to prevent or minimize the harm that affects dam safety.
Affect rare terrestrial organisms ① transplantation ② artificial cultivation ③ establishment of botanical gardens and protected areas.
Figure 4- 1-9 Flooded Area, Resettlement Scope and Urban Resettlement Planning of Three Gorges Reservoir Area
The linear distribution of the flooded area in the Three Gorges reservoir area is different from the flaky distribution of the flooded area in the general reservoir area, which makes the immigrants in the reservoir area relatively dispersed, and almost none of the 356 towns involved in the flooded area are completely submerged, which is beneficial to the resettlement of immigrants in their own county or even their own township, and avoids all kinds of difficulties and sequelae caused by a large number of immigrants moving out and far away. Most of the Three Gorges immigrants can be resettled nearby, which is a major feature of the Three Gorges immigrants.
Three Gorges Immigration Policy: Development Immigration
Advantages and disadvantages of placing near the back:
Advantages: Immigrants are easy to accept if they don't leave their hometown, avoiding the difficulties and sequelae caused by a large number of immigrants moving out and far away. Disadvantages: it is easy to cause excessive pressure on the local ecological environment, such as excessive reclamation of sloping land, destruction of vegetation and aggravation of soil erosion.
Figure 4- 1- 10 Shelterbelt in the Upper Reaches of the Yangtze River
In order to change the situation that the forest vegetation in the middle and upper reaches of the Yangtze River has been greatly reduced and the area of soil erosion has been greatly increased, the state has decided to build a shelter forest system in the middle and upper reaches of the Yangtze River. It is planned to plant trees in 200 counties in this region 1 1 province in 30-40 years, increasing the forest area by 20 million hectares and reducing the area of soil erosion by more than 40 percentage points.
Figure 4- 1- 1 1 Tea Garden in Three Gorges Area of Yangtze River
Slope land with weak acid soil and good drainage conditions is a good condition for planting tea trees. Planting tea trees in the low slope of the Three Gorges area of the Yangtze River can not only achieve good economic benefits, but also maintain soil and water and achieve great ecological benefits.
2. Midstream:
(1) Resource advantages and development measures:
Regional influence and significance of resource advantage distribution
Jianghan Plain, Dongting Lake Plain and Poyang Lake Plain are important production bases of commodity grain, cotton, oil, meat and aquatic products in China.
Rich in mineral resources, iron ore and copper ore in Daye, tungsten ore in Dayu,
Shuikoushan lead-zinc mine and Lengshuijiang antimony mine have formed industrial systems such as metallurgy, machinery and building materials, and are important manufacturing bases in China.
(2) flood in the middle reaches and its regulation
The cause of the flood is:
① Natural causes (decisive factors)
A. Low terrain, slow water flow, siltation and poor drainage;
B. Precipitation is mostly concentrated in spring and summer, and floods make the plain lake area accumulate water, which cannot be discharged into the Yangtze River.
② Man-made reasons (aggravating effect)
A. Excessive deforestation, land reclamation on steep slopes, reduced vegetation on the surface and increased soil erosion;
B. Reclaiming land around the lake and silting up cause the lake to shrink, and the function of regulating flood peak is weakened.
Flood control measures:
A. It is forbidden to reclaim land along the lake, return farmland to the lake, and dredge the lake to enhance the flood storage capacity of the lake;
B. do a good job in flood diversion project. Continue to strengthen and improve the Jingjiang flood diversion project;
C. Take soil and water conservation as the center, build shelter forests and comprehensively develop and control mountainous areas;
D. Build water conservancy projects to give full play to the flood control and sand prevention functions of water conservancy projects.
Background knowledge: the source of flood in the middle reaches of the Yangtze River
The main tributaries above Yichang, Dongting Lake and Poyang Lake in the south and Hanjiang River in the north, are the three main sources of floods in the middle and lower reaches of the Yangtze River. The occurrence time of three floods was affected by the passage of rain belt.
Time position and flood source of rain belt
Generally speaking, the arrival time of each flood is staggered. In May, the Dongting Lake water system and Poyang Lake water system, tributaries of the south bank of the Yangtze River, rose and merged into the Yangtze River.
In June, the main stream of the Yangtze River, the north bank of the Yangtze River and the tributaries of the Han River rose.
In abnormal years, floods come at the same time, and rain belts wander on both sides of the Yangtze River. Floods on the north and south banks of the Yangtze River and floods on the main stream come at the same time.
See Figure 4- 1- 14 Jingjiang section of the Yangtze River (from Chenglingji, Zhicheng, Hubei to Dongting Lake, Hunan)
(1) Reasons for key flood control reach: The river course is especially curved, which is called "nine-bend ileum", and the water flow is not smooth. A large amount of sediment deposition makes the riverbed higher than the riverbanks on both sides, forming a suspended river. In the event of flood, dike burst directly threatens the safety of agriculture, industry, cities, traffic arteries and people's lives and property in Jianghan Plain and Dongting Lake Plain.
(2) Jingjiang regulation measures: building Jingjiang flood diversion project; Perform several bending and straightening projects; Strengthening Jingjiang levee has played a very good role in flood control and navigation.
Thinking: Why is the Yellow River hanging on the ground?
With the widening of the downstream channel, the water flow slows down, and a large amount of sediment is deposited, which gradually raises the riverbed and heightens the riverbanks on both sides, forming a suspended river.
Read Figure 4- 1- 15 Shrinking Dongting Lake.
The reasons for the reduction of lake area in the Yangtze River system are: reclaiming land from lakes; Sediment deposition, lake bed elevation; The increase in industrial and agricultural water consumption has reduced the lake.
The impact of shrinking lake area: the flood peak storage capacity decreased, which aggravated the Yangtze River flood.
3. Downstream area
(1) development task: develop rural economy and comprehensive industries.
General situation and performance of economic development under development conditions
The terrain is mainly plain.
Good agricultural foundation, land of plenty.
Rich in water resources, rivers and lakes are densely covered with silk.
The climate is warm and humid, and the level of rural economic development is high.
Dense population and abundant labor force.
The superior geographical location is the largest comprehensive industrial base in China, with textile, electromechanical, chemical fiber and other industries occupying a prominent position in the country.
Steel, petrochemical products, automobiles and light industry are very important.
Land and water transportation is convenient, and high-tech industries such as microelectronics, electronic information, fine chemicals, new materials and bioengineering have a certain foundation.
(2) Supervision of downstream areas
Environmental problems, water and air quality have generally declined.
Pay attention to the comprehensive management of environmental pollution
Measures to adjust and optimize the industrial structure (the core of environmental pollution control), promote technological progress and innovation, gradually eliminate or transform traditional industries, and vigorously develop high-tech industries and tertiary industries.
By popularizing various environmental protection technologies, strengthening law enforcement, strengthening environmental protection and controlling environmental pollution.
Thinking: What are the advantages and disadvantages of developing industry and agriculture in the lower reaches of the Yangtze River?
(1) Conditions for developing agriculture in the lower reaches of the Yangtze River:
Natural conditions: the climate is warm and humid; The plain is vast; Dense rivers and lakes; Fertile soil and superior natural conditions.
Socio-economic conditions: dense population and abundant labor force; It has a vast market, a long history of development and rich agricultural experience.
(2) Conditions for industrial development in the lower reaches of the Yangtze River:
Advantages: superior geographical location, convenient transportation, dense population, sufficient labor force, strong economic strength, advanced technology and good cooperation conditions.
Disadvantages: lack of resources, especially energy.
Opening the window of knowledge: Pudong development
Opening the window of knowledge: environmental problems in Taihu Lake;
Problem: The water pollution in Taihu Lake is serious, and the eutrophication of Taihu Lake is intensified.
Reasons for the decline of water quality: rapid urbanization and economic development in Taihu Lake area, and a large number of pollutants are discharged into the lake.
Summary: ("Activities" on page 87)
Development advantages and remedial measures for key problems in development
The topography of the upper reaches is very different, the river gap is large, and hydropower resources are abundant. The development of hydropower resources is complex and natural disasters are frequent. Unreasonable development leads to vegetation destruction and soil erosion, and the construction of Yangtze River shelterbelt and water source shelterbelt should be strengthened; Implement the protection policy of closing hillsides to facilitate afforestation, irrigation and planting grass.
A production base of commodity grain, cotton, oil, meat and aquatic products with vast area, fertile land and rich mineral resources in the middle reaches of the plain; The important manufacturing bases in China are seriously flooded, so it is forbidden to reclaim land along the lake, return farmland to the lake and dredge the lake; Continue to strengthen and improve Jingjiang flood diversion project
The lower reaches of the plain are dominant, with warm and humid climate and abundant water resources. The water and air quality in densely populated land of fish and rice and land of silk has generally declined, especially the water pollution represented by Taihu Lake is quite serious. Adjust and optimize the industrial structure; Strengthen environmental protection
Excellent geographical location and convenient transportation, China's largest comprehensive industrial base.