How are rivers classified?

River discharge classification

According to the size of the protected area, large, medium and small rivers are classified.

The protected area of major rivers is over 300,000 mu;

The protection area of medium-sized rivers is between 1 and 300,000 mu;

The protected area of small rivers is less than 6,543,800 mu.

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The Origin of World Water Day

In order to alleviate the contradiction between supply and demand of water resources in the world, according to the principles of water resources protection, development and management in chapter 18 of UN Agenda 265438+20th century, 1993 18 10, adopted by the 47th UN General Assembly.

1996, the World Water Council, composed of experts and scholars on water issues and relevant international institutions, was established and decided to hold a large-scale international conference, the World Water Forum, every three years before and after World Water Day.

The theme of World Water Day over the years is: 1994, it is everyone's responsibility to care about water resources; 1995, Women and Water; 1996, to solve the urgent need of urban water; 1997, is there enough water in the world? 1998, groundwater-intangible resources; 1999, let everyone go downstream; In 2000, 2 1 century water; 200 1 year, water and health; In 2002, water served development; In 2003, water of the future; In 2004, water and disaster.

Not long ago, the United Nations Environment Programme issued a warning: After the oil crisis, the next crisis for mankind is water. Someone once said, "If human beings continue to destroy and waste water resources, then the last drop of water that human beings see will be their own tears."

Reservoir classification

The grades of large, medium and small reservoirs are classified according to their storage capacity.

Large (1) reservoir capacity 1 100 million cubic meters or more;

The storage capacity of large (II) reservoirs is greater than 1 100 million cubic meters and less than 1 100 million cubic meters;

The storage capacity of medium-sized reservoirs is greater than or equal to 0. 1 100 million cubic meters and less than 1 100 million cubic meters;

The storage capacity of small (1) reservoirs is greater than or equal to 654.38 million cubic meters and less than 654.38 million cubic meters;

Small (II) reservoirs have a storage capacity of 65438+ 10,000 cubic meters, less than 1 10,000 cubic meters.

River discharge classification

According to the size of the protected area, large, medium and small rivers are classified.

The protected area of major rivers is over 300,000 mu;

The protection area of medium-sized rivers is between 1 and 300,000 mu;

The protected area of small rivers is less than 6,543,800 mu.

Rainfall classification

Light rain: 24-hour rainfall is less than10mm; 12 hour rainfall is between 0.2 and 5 mm.

Moderate rain: the 24-hour rainfall is between 10. 1-25mm; 12 hour rainfall is between 5.1-15mm.

Heavy rain: 24-hour rainfall is between 25. 1-50 mm; 12 hour rainfall is between 15. 1-30mm.

Heavy rain: 24-hour rainfall is between 50. 1 and 100 mm; 12 hour rainfall is between 30.1-70mm.

Heavy rain: 24-hour rainfall is between 100. 1-200mm; 12 hour rainfall is between 70.1-140mm.

Heavy rain: 24-hour rainfall is greater than 200mm 12 hour rainfall is greater than 140mm.

Leveling of sluice gate

The grade of river sluice is divided according to the flow through the sluice.

The discharge of large river sluice is greater than1000m3/s;

The discharge of medium sluice is greater than1000 m3/s and less than or equal to1000 m3/s;

Small river sluice flow is greater than or equal to 100 m3/s and less than100 m3/s;

Seven flow fields in China.

Haihe river field

Huaihe river flow field

Taihu lake flow field

Songliao flow field

Yellow river flow field

Yangtze river flow field

Pearl river flow field

Dayu controls water.

According to legend, in the Yao-Shun era more than 4,000 years ago, the Yellow River Basin in China suffered a series of disastrous floods. "The soup was cut by the flood, and Hu Aishan Xiangling was swaying, majestic and strange." The whole country was plunged into an unprecedented disaster. Tang Yao presided over a tribal alliance meeting to study the flood problem. At that time, they unanimously recommended Gun, the leader of Xia nationality with a tradition of water control, to preside over Hanshui River. The gun uses the method of "blocking obstacles" to build dams to contain floods. However, the floods are so severe that the dams built are often washed away by floods.

After Tang Yao's death, Yu Shun became the leader of the tribal alliance. On the recommendation of the Parliament of the Tribal Alliance, Yu, the son of Gun, was sent to continue water control. Yu learned the painful lesson of his father's failure in water control, changed the method of simply blocking water with dikes and adopted the strategy of dredging. "Huai Nan Zi Yuan Dao Xun" records: "I definitely blaspheme, based on water." It is said that he took water as a teacher, was good at summarizing the running law of water flow, and used the natural flowing potential of water flowing downwards to control floods according to the situation. He led the people to "dredge the river and guide the stagnation", dredge the river according to the terrain, eliminate the accumulated water, and make the flood and waterlogging return to the river and flow into the sea. After 10 years of efforts, the flood was finally subdued. "Water comes from the ground, and then people will live on the ground."

Dayu's achievements in water control were praised and missed by later generations. During the Warring States period, some people felt: "Wei Yu, I am a fish!" Said if it weren't for Yu, we would be fish and shrimp by now. Later, the legend of Dayu's water control was widely circulated. In the word of mouth of later generations, many important water conservancy activities in ancient times were attached to Dayu. Even some wonders created by natural forces are suspected to be magical and attached to Dayu, adding a bit of myth. It is also said that he was buried in Huiji Mountain in Shaoxing, Zhejiang Province after his death, which is today's Dayu Tomb. Dayu's memory is not only a memory of heroes, but also a call for water management.

Li Bing and Dujiangyan

Li Bing, a native of Qin during the Warring States Period, "can know astronomy and geography". In fifty-one years (256 BC), Zhao Xiang was appointed as the Governor of Shu County, and presided over the construction of the world-famous Dujiangyan water conservancy project on the Minjiang River in guanxian, Sichuan, which effectively promoted the development of local agricultural production.

Dujiangyan hub project is located at the place where Minjiang River enters alluvial plain from valley. From top to bottom along the river, it consists of Baizhang Dike, Yu Zui, Jingang Dike, Sha Fei Weir, Baokoukou and herringbone Dike, among which Youzui, Sha Fei Weir and Baokoukou are the main ones.

These three main projects are an organic whole, which cooperate with each other, complement each other and are indispensable. With the addition of Baizhang dike, flat water tank, herringbone dike, Majiaotuo, sluice and other projects, the ditch has become a scientific and complete irrigation and drainage system, achieving the purpose of "flood diversion and disaster reduction, water diversion and irrigation of fields". All building materials are made of local materials, such as bamboo, wood and pebbles.

The construction of Dujiangyan water conservancy project has made Chengdu Plain "hungry after drought and flood". When there is no famine, the world is called abundance. "It has been more than 2,200 years since Li Bing initiated Dujiangyan. Although it has undergone continuous maintenance and transformation from generation to generation, it still plays a huge role.

Clear rain record

The precipitation records recorded day by day and hour in the Qing Dynasty are now kept in the First Historical Archives of China. Existing rainfall records record the period from the 2nd year of Yongzheng (1724) to the 29th year of Guangxu (1903), *** 180, but there is a gap of six years, which is actually 174. According to the Qing Hui Dian, "Qin Guan Tian Xiang set up an observatory in the southeast corner of Beijing, and recorded all sunny and rainy clouds, thunderstorms, meteors and alien stars. The wind and rain in the mystery are recorded in the diary, which is the record of the wind and rain in the mystery. Write one in the Qing Dynasty and one in China, and pay tribute to it on the first day of February of the following year. " The observatory in this paper is the ancient observatory in the southwest of Jianguomen overpass in Beijing today. The mysterious wind and rain record is the rain record. Rain and shine records take the traditional twelve o'clock as the time standard, and record the rainfall on time, round and round, day and night. Precipitation is divided into three grades: sunny, light rain and moderate rain (or sunny, light snow and light snow). There is no quantitative description, and there is no clear standard boundary between levels, but it provides a complete and systematic series of precipitation conditions. In order to understand the precipitation law in Beijing during 180 years, the measured basis is sought. Compared with the actual rainfall records in Beijing since 184 1, the basic contents of the records in overlapping years are completely consistent.

Rain in summer and autumn

Yu Xia partition domain

Summer rain blocked the wall, but could not stop the girl (Jiangxi)

Summer rain does not climb over the wall (Jiangxi)

Don't cross the river in summer rain (item)

Summer is a hole in the sky, and it is dry (sweet) when it rains.

In summer, the rain in the east building seems to block the wall, but the girl doesn't rain (Hunan)

It rains in summer, so you can divide the wall. It's raining here and sunny there.

There is little rain in summer, and the first frost comes early (Shandong)

There is more rain in summer and less rain in autumn (black)

There is rain in one summer and drought (drought) in three summers

It rains heavily in summer and snows heavily in winter (Geely)

It is rainy in summer (season) and snowy in winter (season) (Inner Mongolia and Xinjiang)

Rainy in summer and little snow in winter (Shandong and Sichuan)

There is more water in summer and more water in winter; Water shortage in summer and winter (Fujian)

It is rainy in summer and autumn frost comes late (Kyrgyzstan)

Summer rain is heavy, and the first frost is late; Less rain in summer and early frost (Shandong)

There is much rain in summer and drought in autumn and winter (Guangxi)

Less summer rain and early autumn frost (North China, Jiangsu, Shandong, Northwest China)

It rains less in summer, hails more, and snows more in winter.

Rain becomes autumn (Anhui)

Autumn rain doesn't cross the ditch, and crossing the ditch will make you shy (cloud)

Autumn rain doesn't go through walls (Fujian)

Ridges separated by fields in autumn rain (Zhejiang, Shandong)

Ash piles in autumn rain (Zhejiang)

Autumn rain, water leisurely (Jiangxi)

Early autumn rain, early frost (Ning)

There is more autumn rain and more snow in winter (Liaoning)

There is more autumn rain and less snow in winter (Inner Mongolia)

Autumn waters are in succession, and winter snow is all over the sky (Su)

There is more autumn rain and less winter rain; Less autumn rain and more winter rain (Fujian)

There are more autumn rains and less spring rains; Less autumn rain, more spring rain (Hebei, Fujian)

There are many autumn rains, but the spring breeze is small (Kyrgyzstan and Jiangsu)

More autumn rain and less spring rain (middle and lower reaches of the Yangtze River, Shaanxi)

It rains in autumn and is not dry in spring (Hebei)

It is rainy in autumn and rainy in spring; There is less rain in autumn and more rain in spring (Hubei)

There are many autumn rains, spring is early and summer is not early (Ning)

There will be more autumn rain, and tomorrow will be early (auspicious)

There is much rain in autumn and drought in winter (Ning)

Autumn is rainy and very dry (Ji)

The autumn rain is torrential, and the spring rain is not dry; There is little rain in autumn and dryness in spring (Kyrgyzstan)

There is much rain and snow in autumn, and it will rain heavily in March and April next year.

Bad roads in autumn, less rain next year (Beijing, Tianjin, Hebei, Shanxi)

It rains after autumn, but it rains less in the future (Anhui)

The river is abundant in autumn, but there is not much rain in the coming year (Guangxi)

The difference between flood disaster and flood disaster

Waterlogging disaster: due to excessive local precipitation, surface runoff can not be eliminated in time, and the accumulated water in farmland exceeds the flood resistance of crops, resulting in the disaster of agricultural production reduction. The reason of crop yield reduction is that the depth of accumulated water is too large and the time is too long, so that the air in the soil is discharged one after another, which leads to insufficient oxygen in the roots of crops, difficulty in breathing in the roots, and the production of toxic and harmful substances such as ethanol, which affects crop growth and even causes crop death.

Flood: Flood is a disaster caused by the surge of water levels in rivers, lakes and reservoirs, the overflow or breach of dams and the entry of guest water. Waterlogging not only caused great disasters to agriculture, but also caused losses to industry and even life and property.

The similarity between waterlogging disaster and flood disaster is that there is too much surface water (or runoff), but the difference is that waterlogging disaster is caused by too much local precipitation, while flood disaster is caused by the entry of guest water.

The change of water conservancy meaning

The word "water conservancy" first appeared in "Little Blue Star Ren Shen" in Lu Chunqiu at the end of the Warring States Period, but the word "water conservancy" refers to the interests of fishing. The word "water conservancy" appeared in the Historical Records of Sima Qian, a historian of the Western Han Dynasty, and began to have meanings such as flood control, irrigation and shipping. 1933 The resolution of the third annual meeting of China Water Conservancy Engineering Society pointed out: "The scope of water conservancy should include flood control, drainage, irrigation, hydraulic power, waterway, water supply, sewage discharge and port engineering." At present, the meaning of water conservancy has been expanded, and water conservancy should also include soil and water conservation, environmental water conservancy, water conservancy and fishery engineering, water resources dispatching management, water administration management and other non-engineering contents. Therefore, the definition of water conservancy can be summarized as: controlling, regulating, guiding, developing, managing and protecting natural water (such as rivers, lakes, oceans and groundwater) by taking various engineering measures or non-engineering measures to alleviate and avoid floods and droughts and meet the water demand of human life and industrial production.

Prevent water pipes from freezing and cracking.

In winter in the north, water pipes are prone to frost crack and water leakage is serious, so special attention should be paid to prevention and inspection. For example, (1) covering sand washed away by flood in rainy season should be replenished before winter to prevent water pipes from being damaged by shallow freezing. (2) Anti-freezing equipment (anti-freezing bolts, anti-freezing wooden cases, etc. ) should be installed on faucets and water pipes outside the house. (3) Where there is ice at home, it should also be wrapped in sacks and wrapped with straw ropes. (4) Doors and windows of houses with water pipes should be pasted, and attention should be paid to indoor insulation. (5) Once the water pipe freezes, don't bake it with fire or burn it with boiling water (that will damage the water pipe and faucet due to sudden expansion). You should wrap the faucet with a hot towel to help thaw it.

Toilet water saving

(1) If you think the water tank of the toilet is too big, you can put a brick or a coca-cola bottle filled with water vertically in the tank to reduce the amount of water flushed each time. However, it should be noted that bricks or coke bottles should not interfere with the movement of water tank components.

(2) The water tank leaks the most, the water inlet rubber is lax, and the water does not stop. After the water is full, it flows away from the overflow hole; If the water stop rubber at the outlet is not tight, the water will keep flowing away and the water will keep entering the inlet pipe.

(3) Using the collected domestic wastewater to flush the toilet, one water can be used for multiple purposes, saving clean water.

(4) Regardless of the size and thickness of the garbage, it should be removed from the garbage passage and cannot be washed away with toilet water.

Bathing saves water.

Take a shower with a shower nozzle: (1) Learn to adjust the ratio of hot and cold water. (2) Don't keep the water in the sprinkler open all the time, let alone open it. (3) Try to get wet from head to toe, then wipe the whole body with soap and rinse it for the last time. Don't wash your hair, upper body, lower body and feet alone. (4) Take a bath with concentration, hurry up, don't be idle, or wash while chatting. Don't have a big water fight with your good friends in the bathroom. Remember: time is water! (5) Don't take the opportunity of taking a bath to "wash clothes and shoes by the way". Take a bath in the bathtub. Pay attention: don't fill it with water. 1/3- 1/4 pots are enough.

Comparison of water prices around the world

China's water price (raw water per cubic meter) is about 0. 1 yuan for urban domestic water, 0. 16 yuan for industrial water and 0.03 yuan for agricultural water. Compared with other consumer goods and foreign water prices, it is obviously low. The industrial water price in Europe and America is generally equivalent to 8 yuan RMB, and the agricultural water price is equivalent to 0.8 yuan RMB. The comparison of water prices around the world is as follows (converted into RMB): Norway, Canada 2. 1 yuan, 3.3 yuan, new york, 3.7 yuan, 4.8 yuan, Sweden, Netherlands 5. 1 yuan, 5.4 yuan, 5.7 yuan, Finland, Belgium, 6 yuan, Italy, 6.9 yuan, Germany 8. 1 yuan, Australia 9.3 yuan. The water price in China is really too low!

What is the flood season?

Flood season refers to the period when the water level rises regularly due to seasonal precipitation and melting ice and snow in the basin. The flood season in China is mainly heavy rain in summer and continuous rain in autumn. Nationwide, the start and end time of flood season is different, which is mainly determined by the climate and precipitation in different regions. South China entered the flood season earlier and ended later; The flood season in northern China entered late and ended early. From May to September every year, the rainfall in the Jianghuai basin is obviously more than that in other months, which is customarily called the flood season. The flood season is the period with the largest precipitation in a year, which is easy to cause floods, so it is necessary to do a good job in flood control.

Wind classification

Level 6: wind speed 10.8- 13.8 m/s, speed 39-49 km/h. The umbrella is difficult to carry, the branches are shaking and the wires are whirring.

Grade 7: wind speed 13.9- 17. 1 m/s, hourly speed 50-6 1 km. The whole tree is shaking, so it is inconvenient to walk in the wind.

Grade 8: wind speed17.2-20.7m/s, speed 62-74km/h. The branch is broken, and there is great resistance for people to advance.

Grade 9: The wind speed is 20.8-24.4m/s and the speed is 75-88km/h, which blows down the straw house and roof tiles.

10 class: the wind speed is 24.5-28.4m/s and the speed is 89- 102km/h, which can blow down trees and destroy ordinary buildings.

1 1 class: the wind speed is 28.5-32.6m/s, and the speed is103-17 km/h, which is destructive, knocking down trees and causing serious damage to general buildings.

12: the wind speed is greater than 32.6m/s and the hourly speed is greater than 1 17km. The waves are huge and destructive.

Drought grade division

Drought is a climatic phenomenon due to long-term lack of rain, dry air and water shortage in soil.

Drought: continuous days without rainfall, reaching 16-30 days in spring, 16-25 days in summer and 3 1-50 days in autumn and winter.

Mid-drought: continuous days without rainfall, reaching 365,438+0-45 days in spring, 26-35 days in summer and 565,438+0-70 days in autumn and winter.

Drought: continuous days without rainfall, 46-60 days in spring, 36-45 days in summer, 765,438+0-90 days in autumn and winter.

Extraordinary drought: continuous days without rainfall, more than 6 1 day in spring, more than 46 days in summer, and more than 9 1 day in autumn and winter.

Classification of tropical cyclones

Tropical cyclone is a huge vortex phenomenon in the atmosphere, centered on the eye of typhoon, which is often calm. Because of the strong updraft around the center, accompanied by violent storms, it is the most dangerous area.

Tropical storm: a tropical cyclone with winds of 8-9 near the center.

Severe tropical storm: a tropical cyclone with wind force of 10- 1 1 near the center.

Typhoon: a tropical cyclone with wind force 12 near the center.

Strong typhoon: tropical cyclone with wind force 12 or more near the center.