Help me with some geography questions.

The Yellow River basin is bounded by latitude 32-42 N and longitude 96- 1 19 E, with a difference of latitude 10 between north and south and longitude 23 between east and west. The basin covers an area of more than 752,000 square kilometers, with a total length of 5,464 kilometers and a drop of 4,830 meters from the source to the estuary. Rocky mountain area accounts for 29%, loess hilly area accounts for 46%, sandstorm area accounts for 1 1%, and plain area accounts for 14%. The natural landscape varies greatly from place to place, especially the largest loess plateau in the world, where soil erosion is very serious.

The Yellow River basin belongs to continental climate. Most areas above Lanzhou are semi-humid areas, while those below Lanzhou are arid areas in northwest, humid areas in south and southeast, and the rest are semi-arid and semi-humid areas. Winter is controlled by Mongolian high pressure, prevailing northerly wind, low temperature and little precipitation; In spring, the Mongolian high weakened, and the western Pacific subtropical high began to extend northward and westward, with the temperature rising and precipitation increasing. In summer, most areas are affected by the western Pacific subtropical high, with southerly winds and abundant water vapor, which is the most rainy period in a year; In autumn, the western Pacific subtropical high gradually weakened, the Mongolian high spread southward, and the precipitation began to decrease, but continuous rainy weather often appeared. The regional distribution of temperature is characterized by a gradual decrease from south to north and from east to west. The annual average temperature is higher than 14℃ in the highest area and lower than -4℃ in the lowest area. The annual extreme maximum temperature in Luoyang basin is 44.2℃, and the annual extreme minimum temperature in Heyuan area is -53.0℃. The precipitation gradually decreases from southeast to northwest. The area with the largest annual average precipitation for many years is Qinling Mountain, which locally exceeds 900 mm, and the station with the largest annual precipitation is Taishan Peak, reaching 1 108.3 mm; The areas with less annual precipitation are Hangjinhouqi and He Lin, Inner Mongolia, which are below 150 mm, and the station with the least annual precipitation is Shanba, Hangjinhouqi, Inner Mongolia, which is only138.4 mm. The rainfall intensity in the upper reaches is small, the duration is long, there are few heavy rains, and the daily precipitation rarely exceeds 50 mm; The rainfall intensity in the middle and lower reaches is high, the duration is short, and there are more heavy rains. There was a rainstorm in Wushenqi, the border of Shaanxi and Inner Mongolia, 1 August, 9771day, and the center of the rainstorm was full of trees. The rainfall during 1400 hours is 1400 mm (survey value), which exceeds the world record. Between Sanmenxia and Huayuankou, 1982, there was a rainstorm from the end of July to the beginning of August. The 24-hour rainfall in Shizhen Town, Yiyang County is 734.3 mm, which is also a rare rainstorm in the Yellow River Basin.

Due to the influence of climate, topography, landforms and other natural geographical landscapes, the hydrological situation of the Yellow River is very complicated, which mainly has the following three characteristics:

First of all, runoff changes greatly in time and space. The ratio of wet year to dry year in the main stream is 2.5~3.5 times, and that in the tributaries is 2.5~40.8 times. The coefficient of variation of annual runoff in each region is 0. 1 ~ 0.53. The difference of runoff depth between multi-water area and low-water area is more than 140 times. The maximum annual runoff coefficient is 0.7 and the minimum is only 0.0 1.

Second, the flood season is long and there are many floods. A year has four flood seasons: rainy season, autumn flood season, autumn flood season and peach flood season, which last for 10 months. The flood season in summer and autumn is called flood season and is formed by rainfall. Its flood sources are above Lanzhou, between Shanxi and Shaanxi, between Longmen and Sanmenxia, between Sanmenxia and Huayuankou, and Dawenhe River Basin. The upstream flood fluctuates slowly and lasts for a long time. The average flood duration at Lanzhou Hydrological Station is 40 days, with the longest 66 days and the shortest 22 days. The flood in the middle reaches fluctuates rapidly, especially in Shanxi and Shaanxi, and its duration is short. The average flood at Longmen Station in the main stream lasted 46 hours, with the longest 80 hours and the shortest 20 hours. The continuous flood usually lasts for 3-6 days, with an average flood of 8 hours, with a maximum of 30 hours and a minimum of 2 hours. Tributary floods are more violent; The flood in the lower mainstream mainly comes from the middle reaches, and its characteristics are related to the source, but it is also influenced by the buildings in the high sediment-laden river bed and beach area, which often causes abnormal changes in the flood evolution law. Ice flood mainly occurs in Ningxia, Inner Mongolia and the lower reaches of the Yellow River, all of which are formed by ice plugs and ice dams. The ice conditions in the lower reaches of the Yellow River are extremely unstable. About one-tenth of the years are not closed, and some years are closed three times. Since the 1960s, the ice situation has changed greatly and the ice disaster has been alleviated due to the ice prevention operation of Sanmenxia and Liujiaxia reservoirs. The reach from Yanguoxia Reservoir to Liujiaxia reaches meandering at 196 1~ 1962, and the upstream of Qingtongxia Reservoir reaches meandering at 1967~ 1968. Taohong is a glacier flood formed by the melting and storage of ice water in the river channel when Ningxia and Inner Mongolia reach the river channel. Peach blossom season flows downstream, with low flood peak and slow fluctuation. After 1972, it is downstream irrigation, Sanmenxia Reservoir stores peach flood, and there is no peach flood peak downstream.

Third, the sediment concentration is high, and the sources of water and sediment are different. Above Lanzhou in the upper reaches of the Yellow River and below Sanmenxia in the middle reaches, there is more water and less sand. There is less water and more sand above Sanmenxia in the middle reaches of the Yellow River. Because the Yellow River flows through the Loess Plateau, soil erosion brings a lot of sediment into the Yellow River. The maximum sediment concentration at Wenjiachuan Hydrological Station of the tributary Kuyehe River reaches 1.700kg/m3. Shaanxi Hydrological Station, the main stream, has an average sediment discharge of 65.438+0.6 billion tons for many years, making it the world's first sediment-laden river. Because of the high sediment concentration in the river, it brings special laws of runoff, confluence, sediment production and transport, resulting in river wandering, drastic changes in river bed and impermanent changes in water level.

Hydrological work of the Yellow River is the basis of harnessing the Yellow River, and it is also an important basis for all the work of harnessing the Yellow River. Hydrological observation of the Yellow River has a history of more than 4000 years. As early as Dayu's flood control period (before 2 1 century BC), trees were used to mark the water level. In the Yin Dynasty (BC 13- BC 65438+ BC 0 1 century), there were records of describing rain and predicting floods by divination. During the Warring States Period, Shen Dao (395 BC ~ 3 BC15) observed the current velocity in the floating bamboo in Longmen of the Yellow River. Rain newspaper system was established in Qin dynasty (2265438 BC+0 ~ 206 BC). In the late Western Han Dynasty (77-37 BC), a rainfall pipe was built and quantitative observation of rainfall began. The sediment of the Yellow River was observed and discussed in the fourth year of the Western Han Dynasty (AD 4). In the Sui Dynasty (A.D. 58 1~6 18), the observation water level of "Shui Ze" was set. In the first year of Wanli in Ming Dynasty (1573), "Tang Ma Bao Hong" was launched. In Qing dynasty (1644 ~1911), water accumulation piles were set up in several places below Lanzhou to measure and forecast water regime, and Luokou observed sediment concentration. The means of transmitting hydrological information in the lower reaches of the Yellow River has also been improved from fast horses to telephones.

From the late Qing Dynasty to the Republic of China, the Yellow River hydrological work developed to adopt modern scientific and technological means. Taian rainfall station was established in 19 12. 19 15, Chengzi Shuiwen Station south of Dawen River was established. From 19 19 to 1933, hydrological stations such as Shanxian, Luokou, Liuyuankou and Zhangjiashan, tributaries of the Yellow River, and water stations such as Xianyang, Jiaokou Town, Yangpingguan and Jinghe Gong, tributaries of the Weihe River, were successively added. During the period of 1933, a serious flood occurred in Shaanxi county, with a peak flow of 22,000 cubic meters per second, which caused serious floods in the lower reaches of the Yellow River, which attracted the attention of the national government to flood forecasting and promoted the development of hydrological work in the Yellow River. During the period of 1937, the Yellow River hydrological observation stations increased, reaching 43 hydrological stations (including river stations, the same below), 29 water level stations and 185 rainfall stations. Later, affected by the war, a large number of stations stopped measuring. 1939 There are only 26 hydrological stations, 4 water level stations and 80 rainfall stations. After the victory of War of Resistance against Japanese Aggression, 1947 restored 60 hydrological stations, 33 water stations and 73 rainfall stations. On the eve of the founding of the People's Republic of China, 1949 still had 44 hydrological stations, 48 water level stations and 45 rainfall stations. During the Republic of China, some hydrological data were sorted out and hydrological analysis and research were carried out. With the improvement of communication technology, special radio stations have been established besides telephones, but the overall situation is still slow, with sparse network, poor equipment, extensive technology and unsystematic data.

After the founding of People's Republic of China (PRC), the Party and the government attached great importance to the Yellow River regulation, and under the impetus of the Yellow River regulation, the Yellow River hydrological work has developed rapidly. Generally can be divided into three stages:

The 1950s. At the beginning of the founding of the People's Republic of China, the Yellow River Committee unified the management of the whole river, and determined that the purpose of harnessing the Yellow River was to "turn harm into benefit, coordinate the upper, middle and lower reaches, and give consideration to the main and tributaries". Hydrological work of the Yellow River is the restoration and development with flood control service as the main task according to the requirements of harnessing the Yellow River. 1955 the second session of the first national people's congress adopted the resolution on comprehensive planning to eradicate flood disasters and develop the yellow river water conservancy, and the work of harnessing the yellow river has entered a transitional stage from flood control to radical treatment. Hydrological work of the Yellow River not only continues to provide hydrological forecast for flood control, but also provides comprehensive services for Yellow River regulation planning, engineering construction, river regulation, irrigation from the Yellow River and soil and water conservation. At the end of 1950s, under the situation of "Great Leap Forward" of the national economy, the hydrological work of the Yellow River also accelerated the pace of construction. 1958 and 1959 carried out technological innovation and revolution, and 1960 proposed "all-round service, ensuring the key points of harnessing the Yellow River, vigorously supporting agriculture, paying equal attention to flood, low water and sediment, and taking into account large, medium and small rivers." Generally speaking, the 1950s was a stage of great development, with a network of hydrological stations initially formed, hydrological tests carried out in an all-round way and test specifications vigorously implemented. Many achievements have been made in experimental observation, analysis and research. All the data compiled over the years have been printed and published, and the data system compiled year by year has also been established. Hydrological information forecasting has played an important role in flood control and ice prevention, laying a good foundation for the further development of the Yellow River hydrological work.

Although it was affected by the temporary difficulties of the national economy and the "Cultural Revolution" in the 1960s and 1970s, it recovered and developed steadily in the later period. During this period, 15 large reservoirs were built on the main stream and tributaries of the Yellow River, and a large number of small and medium-sized reservoirs were also built on the tributaries, which greatly affected the hydrology and natural changes of the Yellow River. In this situation, the harnessing of the Yellow River has put forward requirements for hydrological work, such as perfecting station network, improving test quality, calculating clear water account and sediment account, strengthening hydrological information and forecast, and deeply discussing hydrological change law. On this basis, we should adjust and develop the network of stations, rectify and strengthen facilities, combine soil and ocean, research and create testing tools and instruments adapted to the characteristics of the Yellow River, improve technology, improve the quality of hydrological forecasting, carry out meteorological forecasting and water quality monitoring, increase service items, comprehensively carry out experimental research and hydrological analysis and calculation, and introduce advanced equipment and technology. New progress has been made in various hydrological work.

In the 1980s, according to the national policy of "adjustment, transformation, rectification and improvement" and the spirit of ensuring flood control safety, rational utilization and protection of water resources, with reform as the driving force and flood forecasting as the center, various advanced equipment and technologies were developed and introduced, and an automatic forecasting system was established and gradually modernized.

I. Construction of Station Network

Hydrological station network is the strategic deployment of hydrological work. After the establishment of People's Republic of China (PRC), based on the principle of comprehensive control of flood, runoff and sediment, the old station was restored and a new station was built. 1950, Quanhe Wenwen Station recovered to the highest water level in the Republic of China. 1955 The temperature station, water level station and rainfall station of Quanhe River were 4.7 times, 2.7 times and 13.8 times of those of 1949, respectively. 1956 compiled the hydrological station network planning of the Yellow River Basin, which provided a basis for the scientific and rational construction of the station network. The density of 1960 station network has exceeded the national average level, especially the sediment station network has greatly exceeded the average river. After 1960, in order to adapt to the natural conditions of the Yellow River basin and the new changes in the work of harnessing the Yellow River, the station network planning was revised four times, including three times in the 1960s and 1970s and one time in the 1980s. In the 1960s, due to the temporary difficulties of the national economy and the influence of the "Cultural Revolution", a large number of stations were cancelled inappropriately. In 1970s, it gradually recovered and developed, and several Xiaohe stations were set up. 1990, there were 45 hydrological stations1in the whole river network (including 29 channel stations 129), 60 water stations and 2357 rainfall stations. Among them, 139, 35 and 763 belong to the yellow river commission system. Quanhe Station has 4.28 stations per 10,000 square kilometers, which is 8.23 times that of 1949 with 0.52 stations per 10,000 square kilometers. The rainfall stations in the whole river are 3 1.32 stations per 10,000 square kilometers. The hydrological station system has also been changed from all hydrological stations to the combination of most tributary stations and teams. With the gradual improvement of hydrological station network, the formation and change of hydrological factors such as runoff, sediment and flood in the Yellow River basin have been fully controlled.

Second, the hydrological test

(1) Basic test

Testing is the basis of hydrological work. After the founding of the People's Republic of China, all kinds of basic observations were developed rapidly and comprehensively. In terms of test facilities, in addition to the construction of elevation and plane control, it is mainly to build various test facilities suitable for the characteristics of each station. Hydrological stations using ship survey generally set up gondola ropeways and cable cars (hanging boxes) ropeways in mountain streams, and hydrological stations with narrow sections, stable riverbeds and few floating objects set up current meter ropeways. All hydrological stations that use buoys to measure ocean currents during floods are equipped with buoy dropping devices. 1987, there are 64 crane boats (including 37 yellow river committees), 252 cable cars and current meters (including 94 yellow river committees) in the whole river. In addition to Jiahe Beach Hydrological Station, the Yellow River Committee system is equipped with ropeways, and the lower reaches of the Yellow River are particularly wide and winding. Lanzhou Hydrological Station has also built a semi-automatic current meter cableway, and Ningxia Guyuan Hydrological Station has set up a double-braking electric unicycle cableway. As one of the technical experiences of hydrological services in China, the electric lift cable car has been included in the comprehensive sub-plan of hydrological services promoted by the World Meteorological Organization and recommended to all countries. A few stations that use motorboats have increased their horsepower and installed motorboats, which has improved their flood measuring ability. The largest 600-horsepower shallow-sea survey vessel on the Yellow River was built at Hekou Hydrological Experimental Station, with a length of 40. 15m.

In terms of testing tools and instruments, the necessary testing and measuring tools and instruments of each station should be equipped first, and then gradually improved according to the characteristics of each station. Rainfall observation has developed from rainfall tube to self-recording rain gauge and telemetering rain gauge. 1990, the self-recording degree of rainfall in the whole river has reached 46%, of which the Yellow River Committee system has reached 60%. Water level observation has developed from vertical fixed water gauge to mobile water gauge and various self-recording water gauges and telemetry water gauges suitable for the characteristics of stations. 1987 the self-recording degree of water level in the whole river reaches 20%, of which the Yellow River Commission system reaches 24%. The speed measuring instrument is improved from the general current meter to the sand and grass prevention current meter. The sand measuring tool was improved from a vertical suspended sand sampler to a horizontal sampler, and then an isotope sand measuring instrument was developed. At first, the instruments for sediment particle analysis were sieve analyzer, hydrometer and bottom leaky pipe. In 1960, they were changed to particle size analyzer, and in 1980, they were developed into photoelectric particle analyzer.

Examination norms are the laws and regulations of examination work. In order to unify the test standards and improve the test quality, the Yellow Committee first formulated a simple test procedure at 195 1. 1956, the Interim Specification for Hydrological Stations issued by the Ministry of Water Resources was seriously implemented, supplementary requirements were formulated, and testing methods were improved. In the aspect of flow measurement, all aspects of flow measurement have been tested and studied, and continuous improvement has been made. Since the founding of the People's Republic of China, sediment measurement has been highly valued. In addition to sediment measurement, some stations also carried out precise sediment measurement. 1956 changed to sediment transport rate test according to test specifications. In order to study the law of sediment formation and transport, samples were taken at the Yellow River Commission System 14 Hydrological Station for 1950 particle analysis. By the 1980s, the whole river had developed to 124 stations, including 68 stations of the Yellow River Commission system. The number of particle analysis rooms in Huangwei system was also increased from 1950 to 1 2 in 1980, and then adjusted to 7.

Ice condition is another complicated hydrological phenomenon on the Yellow River. 1960, there are 400 stations in the whole river to observe the ice situation, including the Yellow River Committee system 18 1 station. In order to seriously implement the provisions of the "Hydrological Test Code", in addition to general ice observation, special ice observation was also carried out.

To develop and utilize the water resources of the Yellow River, it is necessary to master not only the water quantity but also the water quality. 1958 was used to test the chemical composition of natural water. 1972 after water pollution monitoring, the chemical composition detection of natural water is combined with water quality monitoring. 1975 established the Yellow River water source protection and water quality monitoring system, and set up a large number of water quality monitoring stations. The analysis method is that the chemical composition of natural water is carried out according to the trial specification of hydrological test, and the pollutant analysis of water quality monitoring is carried out according to the specific specification. In 1980s, all kinds of advanced analytical instruments were gradually introduced, analytical techniques were continuously improved, and the analytical quality reached the international level. Through the investigation and analysis of monitoring data, the main hydrochemical components and salinity distribution of the Yellow River water quality are basically clarified. A large number of data and analysis data show that the water pollution of the Yellow River has become more and more serious since the founding of the People's Republic of China. The length of 1990 reach is lower than Grade III water quality, with 34% of the main stream and 59% of the tributaries.

Hydrological investigation is an important hydrological work to make up for the shortage of hydrological positioning observation. Since the early 1950s, the Yellow River Committee has organized many flood surveys in the main and tributaries of the Yellow River and obtained a lot of valuable information. Such as 1843 Sanmenxia flood in the main stream of the Yellow River, with a peak flow of 36,000 cubic meters per second; Black Port 176 1 year flood with peak flow of 30,000 cubic meters per second; In 223 AD, Longmen Town, yi river was flooded, with a peak flow of 20,000 cubic meters per second; Qinhe Jiunvtai 1482 flood, peak flow 14000 cubic meters per second, etc. , are rare floods that greatly exceed the measured data. In 1980s, the Survey Planning and Design Institute of the Yellow River Committee compiled and published the flood survey results of the whole river 172 section into a book. Gansu, Ningxia, Shandong and other provinces (regions) along the Yellow River will also compile flood survey data.

Due to the continuous enrichment of test work, the continuous strengthening of flood measuring ability, the continuous shortening of test duration, the continuous improvement of test methods and the continuous improvement of test accuracy, the imbalance of water and sediment has gradually decreased, and the scattered water level-discharge relationship has gradually become a regular curve, providing perfect and reliable water, sediment and water quality data for the Yellow River regulation.

(2) Experimental observation

In order to master the characteristics of water and sediment in the Yellow River, in addition to a large number of basic hydrological stations, various experimental observations were carried out to explore the formation and variation of water and sediment.

1953, the Qianleft hydrological experimental station was established for the first time in the estuary to observe and study the law of siltation extension and tail swing in the Yellow River Delta. From 65438 to 0956, large-scale water surface evaporation stations were established in Shangquan, Sanmenxia and Sansheng successively, and the relationship among reservoir water surface evaporation, general evaporator and natural water surface evaporation was studied, which provided data for calculating large-scale land surface evaporation. During the period of 1957, a riverbed evolution test team was set up in Huayuankou wandering reach to observe and study the fluctuation law of riverbed erosion and deposition. Observation teams are set up in the naturally curved reach below Gaocun and in the artificially controlled and semi-artificially controlled curved reach to observe the changing law of the curved reach. From 65438 to 0958, Zizhou Runoff Experimental Station was established in Chabagou of Loess Plateau in northern Shaanxi, and the formation and change of runoff in loess area and the influence of soil and water conservation were observed and studied. In the same year, Sanmenxia Reservoir Hydrological Experimental Station was established. With the construction of large and medium-sized water conservancy projects such as Weishan, Yanguoxia, Bapan Gorge, Qingtongxia, Tianqiao and Bajiazui, experimental stations (teams) have been established one after another to carry out observation and research on the law of sediment movement in the reservoir area. A total of 14 experimental stations (teams) were established, various hydrological test data were measured, and a large number of analysis reports and monographs were written. These achievements have played an important role in the Yellow River regulation planning, river regulation, reservoir construction management and application, and estuary regulation.

(3) data compilation

In the early days of the People's Republic of China, according to the urgent need of the Yellow River regulation planning, the basic hydrological data of the Yellow River before 1953 were systematically sorted out and published in 1956. On this basis, it is determined to sort out the data year by year from 1954, and establish four steps: on-site sorting, centralized auditing, auditing and compilation, and printing and publishing to ensure quality and improve work efficiency. The annual examination materials are generally published every other year. In addition to the implementation of national unified regulations, the reorganization method is supplemented in combination with the characteristics of the Yellow River. 1976 tried to reorganize computers, and 1984 introduced computers from abroad. Since then, the preparation and construction of hydrological data database has been officially started, which has promoted the reform of data reorganization.

Hydrological test data reorganization: Since the reorganization of the test data in Sanmenxia reservoir area in 1960, the reorganization of the test data has been carried out one after another. At the same time, the data of Xiaohe Station have been reorganized, and the hydrological characteristic values have been counted five times on the basis of the reorganized data. In the early 1970s, the eigenvalue of the Yellow River Basin was calculated, and the original area of the Yellow River Basin was changed from 745,000 square kilometers to 752,443 square kilometers, and the original river length was changed from 4,845 kilometers to 5,464 kilometers.

Up to 1990, * * * has compiled 368 volumes of various hydrological data, which are used not only by the relevant units of the Ministry of Water Resources and the Yellow River Commission, but also by other 165 units and departments.

Three. Hydrometeorological information forecast

Intelligence work. In 1950s, the network of hydrological stations reporting floods to the Yellow River Flood Control Headquarters increased from 1949 to 404 1959. As a means of water regime transmission, the communication network combining public telegraph, telephone and special wireless telephone was adopted from the beginning. The method of water regime shooting is improved from simple routine shooting to substandard shooting. Basically formed a relatively complete hydrological information system. In the 1960s, the hydrological station network declined sharply. 1970 began to pick up and stabilized at around 500 in the late 1970s. In view of the lesson that hydrological information was useless during the Huaihe River flood in August 1975, the Yellow River Committee established a special wireless communication network below Sanmenxia. Since the early 1980s, an automatic telemetry system has been established between Sanmenxia and Huayuankou. At present, the hydrological department of the Yellow River Committee has established an automatic receiving, processing and transmission system of rain and water information, which greatly improves the timeliness of water information transmission.

Hydrological forecast. 195 1 to forecast the flood peak of the lower Yellow River. Forecast of rainfall, runoff and flood process in the middle and lower reaches of the Yellow River from 65438 to 0955; 1959 develops upstream, and comprehensively carries out flood, low water, ice conditions, long-term, medium-term and short-term forecasts. From the late 1960s to the 1970s, we strengthened the research on forecasting technology by cooperative means, and organized great cooperation among scientific research units, universities and the Yellow River Committee to study and improve the long-term rainstorm and flood forecasting in the Yellow River. At the end of 1970s, the relevant provinces (autonomous regions) in the basin were organized to cooperate with hydrological and water conservancy departments, and a flood forecasting system for the lower reaches of the Yellow River was established. 1975, the Yellow River Committee set up a meteorological agency, which changed from relying entirely on meteorological departments along the river to carrying out meteorological forecast by itself, and established a long-term precipitation forecast consultation meeting before flood season and joint defense of rainstorm in flood season with relevant provincial meteorological stations, which combined meteorological forecast with hydrological forecast and increased the forecast period of flood forecast. After 1982, computers were gradually popularized, and an automatic telemetry online real-time flood forecasting system was established between Sanmenxia and Huayuankou, which improved all forecasting methods mainly based on Sanhuajian forecasting and improved the forecasting accuracy. The weather forecast has also established an automatic receiving and processing system for satellite cloud images, rain radar and various meteorological information, and has begun to study and establish an expert system to improve forecasting methods and improve forecasting accuracy. The hydrometeorological forecast of the Yellow River began to approach the international advanced level.

Since the founding of the People's Republic of China, the hydrometeorological information forecast of the Yellow River has provided about 3 million station information and more than 4,000 station forecasts for the flood control and ice prevention of the Yellow River over the years, especially in the flood areas of the Yellow River 1958, 19865, 438+0 and 1982, which provided accurate and timely flood information and forecast, and made the flood control work adopted.

Four, hydrological calculation analysis and research

This is the basis of planning and construction of water conservancy projects for harnessing the Yellow River, and it is also an important scientific basis for harnessing the Yellow River. A lot of work has been done since People's Republic of China (PRC) was founded. 1954 When compiling the Technical and Economic Report on the Comprehensive Utilization Planning of the Yellow River (hereinafter referred to as the Technical and Economic Report on the Yellow River), a comprehensive and systematic hydrological analysis and calculation were carried out on the main and branch flows of the Yellow River, and the formation and variation laws of precipitation and runoff in the Yellow River basin were analyzed and studied. Later, when revising the supplementary plan for harnessing the Yellow River, the related contents were further analyzed and calculated. In 1960s, the main hydrological data of main hydrological stations in the whole river were unified, and it was determined that the annual average runoff of Shaanxi County was 42.35 billion cubic meters, and the annual average sediment discharge was 65.438+600 million tons. The analysis and research of water and sediment is centered on the radical cure of the Yellow River flood and the reconstruction of Sanmenxia Reservoir. In view of Qian Ning's statement in 1959 that the main component of sediment in the lower Yellow River is coarse sand with a particle size greater than 0.05 mm, the source of coarse sand was investigated after 1965. During the same period 1962 to 1965, the ice jam in the upstream Liujiaxia-Yanguoxia reach was observed and studied, and the calculation method was put forward. After entering the 1970s, according to the instructions of the Ministry of Water Resources and Electric Power (hereinafter referred to as the Ministry of Water Resources and Electric Power), the Yellow River Management Committee formulated a regulation plan for the Yellow River, and analyzed and studied the variation law of water and sediment, which not only clarified the source of coarse sediment in the lower reaches of the Yellow River, but also studied the law of sediment transport in the Yellow River. Through analysis and calculation, it is determined that the possible catastrophic flood flow at Huayuankou in the lower reaches of the Yellow River is 55,000 cubic meters per second. At the same time, the main historical floods in Sanmenxia and Huayuankou were analyzed, and the ice flood in the lower reaches of the Yellow River was systematically studied, and many valuable results were obtained. In the 1980s, when the Yellow River Regulation and Development Plan was revised, the water and sediment were analyzed and calculated again, and the laws of sediment movement, historical floods, ice conditions of the Yellow River, water resources of the Yellow River and climate of the Yellow River basin were comprehensively analyzed and written into a monograph. The rheological properties of muddy water with high sediment concentration and the observation of frazil ice and ice jam in meandering section were also carried out, and many valuable results were obtained.

Since 198 1 wrote an ice paper and participated in an international ice seminar, it has created a new situation for the Yellow River Committee to participate in international academic exchanges. A number of hydrological research achievements have been exchanged internationally for more than ten times, and advanced hydrological research achievements from abroad have been introduced continuously, which has promoted the development of hydrological research work in the Yellow River.

Since the founding of the People's Republic of China, the Yellow River hydrology, as the basis of disaster prevention and mitigation and the development and utilization of water resources, has been highly valued by the party and the government, and has invested a lot of money. By 1990, the system expenditure of the Yellow River Committee alone reached 220 million yuan. Established a hydrological team with skilled business and excellent thinking. By 1990, there were more than 4,680 employees in the whole river, including more than 2,500 people in the Yellow River Commission system, and a relatively complete hydrological system of the Yellow River has been built. The majority of hydrologists in the Yellow River, especially those who work in the front line of hydrological forecasting, have worked hard and struggled. They struggled with rainstorm, flood, sediment and ice under very difficult conditions, and 3 1 person in the yellow river commission system alone gave their precious lives. In the past 40 years, the hydrological work of the Yellow River has provided a lot of hydrological data, hydrometeorological information, forecasting and hydrological analysis research results for the Yellow River regulation, and has embarked on a road of hydrological development with the characteristics of the Yellow River, which has played an irreplaceable role in the regulation and development of the Yellow River and the economic development of the basin. However, the Yellow River is the river with the most complicated hydrological changes and the most difficult experimental conditions in the world. Especially with the harnessing of the Yellow River and the development of basin economy, the hydrological situation of the Yellow River has changed greatly, the quality of hydrological forecast is far from meeting the needs, the calculation of incoming water and sediment is not sufficient, and many problems in hydrological laws, especially the new changes, have not been solved. Hydrologists in the Yellow River must spare no effort and make unremitting efforts to further improve the station network, strengthen forecasting, conduct in-depth research, work harder, overcome difficulties, and continuously develop and improve the Yellow River hydrological cause on the basis of existing achievements.