Urgent questions about the Yellow River and Ode to the Yellow River ~

In recent years, the runoff in the source area of the Yellow River has been greatly reduced, and the related ecological environment has been deteriorating, such as increasing soil erosion, increasing the buried depth of frozen soil, land desertification, shrinking lakes and wetlands, melting glaciers, grassland degradation, rampant rodents and pests, and sharp decline in species and quantity, which have seriously threatened the healthy life of the Yellow River. In order to solve the problems existing in the source area of the Yellow River, the Yellow River Research Association held a seminar on runoff and ecological changes in the source area of the Yellow River in Zhengzhou, Henan Province on July 7-8, 2004. At the meeting, more than 100 academicians, experts and scholars from water conservancy, geology, engineering, environment, grassland and other fields all over the country had a heated discussion on the existing problems, development trends and solutions of runoff and ecological changes in the source area of the Yellow River. Comrade He of Huang Wei's National Science Bureau collected and sorted out the speeches made by academicians such as Huang at the meeting, and now they are published in a concentrated way for readers.

Academician Huang:

This paper mainly discusses the changes of meteorology and climate in the source area of the Yellow River. Specifically, there are three aspects: first, the interdecadal (interannual) change of climate in northwest China and the upper reaches of the Yellow River; The second is the change of runoff and precipitation in the source area; Third, what will happen to the climate in this area in the future.

The Yellow River is our mother river. Due to climate change and the sharp increase of industrial and agricultural water consumption, the runoff in the lower reaches of the Yellow River has been greatly reduced or even cut off, which has seriously affected the industrial and agricultural water consumption in some parts of North China and the lives of urban and rural people? Use water.

Affected by climate change, severe drought has occurred in northern China since 1977, causing great economic and food losses. Among all disasters, weather disasters account for more than 70%, and drought disasters account for about 50%. In 1990s, the Yellow River was cut off for a long time. In recent years, water diversion measures have been taken to prevent this phenomenon. Our research is mainly based on the meteorological observation data of meteorological stations in the upper reaches of the Yellow River and other areas in recent 50 years and the runoff data of hydrological stations in the upper reaches of the Yellow River for more than 40 years.

First, talk about the interdecadal (interannual) variation of precipitation in western China. In 1950s and 1960s, the annual precipitation in this area was less. Since 1970s, the precipitation in the northwest and east has increased. By 1980s, the precipitation in most parts of northwest China had increased. Precipitation increased a lot in the 1990s. However, we should see that the climate change in the source area of the Yellow River is different from that in the northwest, but similar to that in the western part of North China and Guanzhong area, so the precipitation in this area decreased greatly in the 1990s, and the runoff also decreased.

In summer, the precipitation in northwest China is concentrated from May to September every year, and summer precipitation accounts for a large part of the annual precipitation. In 1950s and 1960s, the precipitation in northwest China was relatively low, and increased from the late 1970s, especially in 1980s, while the precipitation in the source area of the Yellow River was relatively good. However, when the precipitation in the northwest increased in the 1990s, the precipitation in the source and upper reaches of the Yellow River was less.

In the 1950s and 1960s, the spring in the northwest was dry, but in the 1980s, the precipitation in the northwest began to increase, and in the 1990s, it increased a lot. However, after the 1970s, great changes have taken place in the climate of China. After 1977, North China became dry and precipitation in Northwest China began to increase. After 1977, the precipitation in the source area of the Yellow River increased to the end of 1980s and began to decrease in 1990s.

There is relatively little precipitation in autumn, but the change is the same. In the 1950s and 1960s, there was less precipitation in the northwest. In the 1970s, the precipitation in the eastern part of northwest China began to increase, and in the 1980s and 1990s, the precipitation in the upper reaches of the Yellow River was similar to that in Guanzhong area, but overall it was still less.

It mainly snows in winter. There was a lot of snowfall in the northwest in the 1950 s and a lot in the 1960 s. The 1970s was good, the 1980s was even better, and the 1990s was ok.

Historically, the precipitation in northwest China has obvious interdecadal (interannual) changes. After the dry season in 1960s and 1970s, the annual precipitation has increased since 1980s, especially in spring, summer and autumn. The annual (interannual) variation of annual precipitation anomaly or seasonal precipitation anomaly in the upper reaches of the Yellow River is obviously different from that in the northwest. In 1990s, the annual precipitation in this area decreased, especially in summer and autumn.

Although the precipitation in the source area of the Yellow River was relatively high in 1980s, it decreased in 1990s. Judging from the temperature, evaporation has a great relationship with temperature. Since 1977, the temperature has been rising all over the country in spring and summer. Except for the Zoige area in the upper reaches of the Yangtze River and the Yellow River, the temperature in other areas has increased, with the highest increase in Northeast China and North China. The national temperature in autumn and winter has also increased significantly. The increase of temperature increases evaporation and decreases runoff. The rising temperature causes the snow line to rise by 30 ~ 60m；; ; In addition, rising temperatures are conducive to the melting of glaciers. Since 1960s, the glacier area in the whole northwest region has decreased by about 1 400 km2.

The above are the precipitation and temperature changes in the whole northwest and upstream source areas, that is to say, the ten-year (international) climate change in the source area of the Yellow River is different from that in the northwest. After the late 1970s, precipitation in northwest China increased and decreased in 1990s.

Let's talk about the changes of precipitation, temperature and runoff in the whole region, including Maduo, Dari, Xinghai, Zoige and Hongyuan. We mainly studied the changes of precipitation, temperature and runoff in Tangnaihai basin, including Hongyuan, Zoige, Maduo, Dari and Xinghai. The average annual precipitation in this area is 522 mm, but it changes greatly within the year (inter-year), and the annual change is about 4-7 years. Precipitation mainly increased in 1970s and 1980s, and decreased in 1990s. Judging from the temperature, including the five stations representing the upper reaches of the Yellow River, the temperature has risen a lot, and the annual increase is about 65438 0.0℃, which is relatively large. In the 1960s, the temperature anomaly was -0.5℃. What was it in 2000? +0.5 ℃,? It has increased by about 1℃, which is similar to that in North China.

The runoff of Tangnaihai Hydrological Station was relatively large in 1950s and 1960s, which was about 20 billion m3, but decreased to 654.38+0.50 billion m3 in 1990s. The cutoff of the lower Yellow River is not only related to the increase of industrial and agricultural water consumption, but also related to the decrease of upstream water inflow.

Runoff and precipitation in this area have the same cycle, and the interannual variation cycle is 3~7 years. Wavelet analysis of the discharge above Tangnaihai shows that the period of runoff change is about 20 years from the age (international). Runoff was relatively large in the early 1970s and 1990s, but decreased after 1990s. Anomalies began to be negative in the early 1990s and may become positive in a few years. Therefore, no matter from the interannual change or the ten-year (interdecadal) change trend, the runoff in the source area of the Yellow River will increase.

The situation of other upstream stations is as follows: Maduo is close to the birthplace of the Yellow River, and the precipitation has not changed much, which is basically the same as that of the whole region; Although there are some fluctuations in Dari Station, the fluctuations are not too great. Of course, judging from the temperature, the temperature in Maduo and Dari stations is rising.

Evaporation is related to temperature. The evaporation at Maduo Station has increased, the evaporation at Dari Station has also increased slightly, and the ground temperature has also increased, but the extent is small. The precipitation at Tangnaihai Station increased in 1980s and decreased in 1990s, but the decrease was not significant, but the runoff changed obviously. The flow change trend of Lanzhou Station is similar to that of Tangnaihai Station. Due to the increase of average temperature and evaporation at Tangnaihai and Guide stations, human activities have reduced the flow of Lanzhou Station to a greater extent than Bitangnaihai Station. From the wavelet analysis, the runoff of Lanzhou Station has experienced a process of less, more and less, and has experienced a continuous reduction stage of 13 years since the 1990s, and is now at a turning point. The interannual variation of runoff is also in a turning period from small to large.

The above analysis shows that the average precipitation in the source areas of the Yellow River above Tangnaihai, including Hongyuan, Zoige, Maduo, Dari and Xinghai stations, has not changed much. Although the annual precipitation has changed since the 1960s, it is not obvious. From the early 1960s to the early 1970s, there was relatively little precipitation. From the mid-1970s to the early 1990s, there was relatively more precipitation. Since the 1990s, there has been less precipitation. In 1980s and 1990s, the temperature in this basin was warmer, and the temperature rose obviously, which was 65438 0℃ higher than that in 1960s.

These changes of precipitation and temperature can also be seen from the observation values of Maduo and Dari stations in the upper reaches of the Yellow River. According to the data of Tangnaihai Hydrological Station, from the mid-1960s to the early 1990s, the runoff in the upper reaches of the Yellow River was relatively large. However, due to the obvious increase in temperature, evaporation, industrial and agricultural water consumption and urban and rural people's water consumption, the runoff in the upper reaches of the Yellow River has shown a sharp downward trend since the early 1990s. The discharge in the upper reaches of the Yellow River has a great relationship with the precipitation in this basin, and the correlation coefficient can reach 0.75, indicating that the discharge in the upper reaches of the Yellow River mainly depends on precipitation. However, according to the precipitation data, although the precipitation in the upper reaches of the Yellow River decreased in the 1990s, it was not obvious. So, why is the flow in the upper reaches of the Yellow River falling so fast? This can only show that on the one hand, evaporation has increased, on the other hand, water consumption of industry, agriculture, animal husbandry and urban and rural residents in the basin has increased.

Finally, what changes will happen to the climate in the source area of the Yellow River in the future. In the future, due to the development of industry, more and more greenhouse gases will be emitted, resulting in an increase in the concentration of carbon dioxide in the atmosphere. Now the mass fraction of carbon dioxide in the atmosphere is 30× 10-6~40× 10-6 higher than that in the early 1980s. According to the book Global Warming, in 2 100, the prediction of surface temperature rise range is 2℃, 3℃ and 1℃. Generally speaking, the temperature is rising, but the extent of the increase is uncertain.

According to the calculation made by my student, Dr. Gao, using the climate value of the Institute of Atmospheric Research of China Academy of Sciences, the temperature in the source area of the Yellow River will increase and the precipitation will also increase in the next twenty or thirty years. Although the precipitation in the upper reaches of the Yellow River may increase according to the results of wavelet analysis of runoff in the upper reaches of the Yellow River and the extrapolation of the results of global model numerical forecast, the temperature rises obviously, indicating that the evaporation in the upper reaches of the Yellow River will continue to increase, and the industrial and agricultural production and urban and rural water consumption in the upper reaches of the Yellow River may also increase, which may lead to further decrease of runoff in the upper reaches and further degradation of the ecology in the source area of the Yellow River.

In my opinion, to adapt to climate change and sustainable development, the upper reaches of the Yellow River should not only consider the previous climate and environmental changes and current situation, but also consider the climate and hydrological changes in the next few decades and hundreds of years. In the future, the upper reaches of the Yellow River will heat up, the ecology will deteriorate and the water consumption will increase. To realize sustainable development, we must study the climate, hydrology, ecological environment and sustainable development in the upper reaches of the Yellow River as an important systematic scientific problem. I once appealed to the Committee on Population, Resources and Environment of the Chinese People's Political Consultative Conference on this issue, and they also agreed with this view.

Academician Li Jijun:

10 years ago, I visited the upper reaches of the Yellow River many times in order to study ancient glaciers, the Qinghai-Tibet Plateau and long-term climate and environmental changes. I'd like to make some comments about this meeting.

With the increase of global temperature and the change of monsoon, according to geological and climatic records, the general rule is that high temperature and high humidity are compatible, but there is a matching relationship between temperature and precipitation, such as high temperature and high humidity and low temperature and low humidity, that is, drought, high temperature drought and low temperature and cold humidity. For tens of millions of years, northwest China has been dominated by the combination of high temperature and high humidity, low temperature and low humidity. According to this forecast, the upper reaches of the Yellow River will not continue like this and will get wet. Seven years ago, one of my graduate students came to a conclusion when studying the desertification trend in arid areas in northwest China: the real arid areas are in western Xinjiang and Hexi Corridor, where the river runoff has obviously increased since the end of 1980s, but the semi-arid and semi-humid areas in eastern Qilian Mountain are obviously semi-dry. How do you explain this? I think it's mainly caused by evaporation. The evaporation in real arid areas also increases with the increase of temperature, but the local circulation is strong and glaciers are melting. Maybe there is something wrong with the high wind and water vapor. The same performance is that the runoff on the mountain increases, but which one is dominant is still unclear and worth studying. These factors make the runoff in Xinjiang and the west of Hexi Corridor increase by more than 10%. The year before last, Mr. Shi Yafeng noticed this problem and called it climate change, and made a serious study on it, which aroused widespread concern in academia and society. At the same time, the drought in the northern semi-arid areas, including Longdong, is remarkable, and I quite agree that the strengthening of evaporation has led to this change.

As the global temperature rises and the monsoon intensifies, the inland of Asia is getting wet, which is what geological records tell us, but I didn't expect the arid areas to get wet soon. In semi-arid and semi-humid areas, due to the rapid increase of evaporation, the soil loses moisture, the atmospheric circulation is not adjusted, and the water vapor from the ocean is not enough to significantly increase precipitation, resulting in drought. Peat in all parts of the Qinghai-Tibet Plateau was discovered after Holocene temperature rise, precipitation increase, temperature rise and vegetation improvement. The climate during the Ice Age was very cold and dry. In this case, the vegetation was very poor, and of course there would be no peat. How long it will take to change, but also specific research. Now the rainfall in this part of Xinjiang is increasing, the melting of glaciers, the increase of precipitation, the local circulation and the proportion of water vapor transported at high altitude really need to be studied in detail.

I agree with Academician Ugly that there won't be much water if ecological destruction is stopped. The key is to look at the big environment and climate. So did it stop doing ecological things? You should do this. We have been to the upper reaches of the Yellow River several times. In the 1980s, people in Maduo said: Although this place is very poor, our per capita income in Qinghai Province is very high. Why? That is, herding sheep, there are many sheep and the output value is high. However, I heard that it will not work in recent years. There are too many livestock, and the grassland is overloaded, so I can't get by myself. Academician Zhang Xinshi was invited to give a speech at the 50th anniversary celebration meeting of Lanzhou Branch held last month. He insisted on stopping all primitive nomadism and replacing it with artificial grassland grazing, because primitive nomadism had extremely low benefits and destroyed the ecology. Of course, there are still problems of economic and policy adjustment in how to do this, but we cannot allow pastoral areas to increase the number of livestock indefinitely. With the development of our country, industrialization and urbanization will eventually solve this problem.

The upper reaches of the Yellow River is the main formation area of the Yellow River runoff, including 30 billion m3 in Lanzhou and 20 billion m3 in Tangnaihai. Generally speaking, Lanzhou is only the mouth of the Qinghai-Tibet Plateau. Qinghai-Tibet Plateau is the first step of China landform. In the second step, the Loess Plateau began to enter the water-consuming area, going north to Yinchuan and Baotou, and reaching the desert Gobi. Water consumption is even greater. After turning a big bend, it entered the loess area and the sediment increased greatly. After the structural pattern of China arrived in the west, its direction changed: northeast to the east of Luoyang and northwest to the west of Luoyang. From the Weihe River valley to Lanzhou, Xining, the northern foot of Qilian Mountain, and then to the northern foot of Tianshan Mountain, the present industrial belt is arranged in this way, and the ancient Silk Road is also along this direction. In the future, the development of industry, agriculture and all walks of life in northwest China will need water, and water should also be concentrated in this place.

Now there is an idea that if water is to be blocked in Tangnaihai, there will be as much water as Inner Mongolia needs, and Guanzhong needs water, and the industrial belt is here, so that the economic role of water can be fully exerted. This is beside the point. We should study the Yellow River well. Our water is very scarce, especially in the north. When a graduate student was defending, he calculated an account, which showed that each kilogram of wheat in northwest China consumed nearly 3 m3 of water. This kind of agriculture is extremely backward and should be abolished in the end. The population should be concentrated in places with better living conditions, so that the ecology can also be protected. The same is true of the upper reaches of the Yellow River. It is not easy for herders to live in nomadic tents. They can move to other places, because primitive nomadism will inevitably bring ecological damage.

Ugly academician Fan Ji:

I mainly talk about three issues: first, the characteristics of climate change in the source area of the Yellow River, characterized by drought; Second, what caused the drought; Thirdly, the change of net inflow of water vapor transport at the boundary of the source region is analyzed from the atmospheric water cycle, and then the turning point of precipitation and water vapor transport is analyzed.

Characteristics of climate change in the source region of the Yellow River: The annual average temperature in the upper reaches of the Yellow River increased significantly from 196 1 to 200 1. I think it is obviously warming up in our country except the southwest, because this warming up is a ten-year (international) time scale. The global warming we are talking about is the global average temperature, but the response of different regions to the global average temperature rise is not exactly the same. For example, the warming in the east of Qinghai Province is more serious than that in the west.

The change trend of precipitation in the upper reaches of the Yellow River is decreasing, but it is not obvious. From 196 1 year to 200 1 year, the trend slows down and there is no year-to-year change (inter-year). Here's a problem. Generally speaking, from a global perspective, with global warming, water evaporation intensifies and rainfall increases. However, due to the different reactions in different regions, the temperature here has increased and the precipitation has decreased.

The evaporation in the upper reaches of the Yellow River has greatly increased. With the change of evaporation, it is generally believed that the temperature increases and the evaporation increases. But not long ago, researcher Chen of Ningxia Meteorological Bureau did a job to analyze the changes of temperature and evaporation at all stations in Ningxia. The results showed that although the temperature increased obviously, the evaporation decreased. Mr. Ye Duzheng said that he also found this phenomenon from foreign materials. So what caused it? Chen made a further analysis, pointing out that evaporation is not only affected by temperature, but also by wind speed. So, Chen counted the changes of wind speed in Ningxia, and found that with the increase of temperature, the wind speed decreased obviously, so he put forward a preliminary idea, that is, the influence of wind reduction on evaporation exceeded the increase of temperature.

Generally speaking, the temperature rise in the upper reaches of the Yellow River is well known. With the increase of temperature, the decrease of precipitation and the increase of evaporation, the drought is very obvious.

What is the cause of the drought? It can be seen from the perspective of atmospheric water vapor transport. Because of how the Yellow River water reaches the sky, the local precipitation is actually a result of the global water cycle. The global water cycle is not only an important material cycle, but also an energy cycle. Solar energy converts liquid water on the ocean, which accounts for 70% of the earth's surface area, into water vapor, which is transported to various places with the atmospheric circulation, converted into precipitation under appropriate conditions, and releases heat. This is actually a process.

When analyzing the source area of the Yellow River, we actually draw this area according to latitude and longitude, and look at the amount of water vapor transported through the boundary. According to NCEP reanalysis data, precipitation should actually be like this: how much water vapor flows in, how much water vapor flows out, how much water vapor evaporates from the ground, and the water vapor content in the air has little change. This is precipitation. If little or no water vapor enters, no water vapor flows out, and the ground does not evaporate, there can be no precipitation. In addition, precipitation is related to the water vapor conversion rate in this area. With so much water vapor flowing in, precipitation and evaporation will flow out. If the precipitation efficiency is high, the outflow will be reduced. Why am I bringing this up? Because this is related to artificial precipitation enhancement. So much water vapor goes in and evaporates, which may affect precipitation, so it will affect outflow. I hope this method can be used to diagnose the efficiency of artificial precipitation enhancement in the future.

QV variation of the whole layer in the upper reaches of the yellow river. It is found that the net water vapor transport in the north-south meridional direction has a very good synchronous effect with precipitation, which is completely in phase, positively correlated in the north-south direction and negatively correlated in the east-west direction. At present, the precipitation in the upper reaches of the Yellow River is inconsistent with that in the whole northwest region. During this time, the northwest became wet, but the upper reaches of the Yellow River dried up, which is not completely consistent. Judging from the situation of water vapor, most of the water vapor in the northwest is brought by the west wind, so the water vapor transport in the east-west direction increases. However, according to the data, the east-west water vapor transport is negatively correlated with the precipitation in the source area of the Yellow River. The west border flows in and the east border flows out. Integrating the north-south boundary of the whole source region of the Yellow River, it happens that the inflow of water vapor is consistent with the change of precipitation.

Conclusion: In order to explore the influencing factors of regional anomalies in the upper reaches of the Yellow River, the interannual variation of the net inflow of water vapor at each side of the box-shaped boundary in the source region of the Yellow River is calculated, and the correlation between water vapor transport at each side of the box-shaped boundary in the source region and precipitation in the source region is analyzed. The results show that the water vapor in the southern and northern boundary layers of the source region is significantly correlated with the precipitation in the source region, and the correlation coefficient exceeds the reliability standard of 90%. Further discuss what factors are related to the water vapor transport in the source region of the Yellow River, that is, they are closely related to the south or north of the western Pacific subtropical high and the strength of the monsoon. Therefore, we come to the conclusion that the decrease of precipitation is a reflection of the interdecadal change of the whole atmospheric circulation. In this case, it is difficult to take any measures to increase precipitation. If we only look at the source area of the Yellow River, there are only two people per square kilometer in that area, so it is difficult to talk about large-scale industrial and agricultural production. You can consider moving people out instead of overgrazing. But such improvement can't increase the precipitation. What can be done to increase precipitation? Is there nothing you can do? The artificial precipitation enhancement in Qinghai Province since 1998, according to the investigation and local people's reflection, the effect of precipitation enhancement is obvious in the operation area and time, but at present, the annual artificial precipitation enhancement fund in the upper reaches of the Yellow River and around Qinghai Lake is only 5 million yuan, and it is only implemented in a short time in summer, so it should be said that it is something we can do to carry out artificial precipitation enhancement in the source area of the Yellow River under appropriate circumstances.

Artificial precipitation enhancement can increase the precipitation range, that is, 10% ~ 15%. Can't exaggerate, it can't solve the whole drought problem.

Academician Fu Yunbin:

Today, I mainly want to introduce the achievements of the national key basic research planning project that has just passed the acceptance, namely, the evolution of human settlements in China and the prediction of drought trend in northern China. According to the results of this project, from the past, present and future of drought in northern China, some information is provided for the discussion of runoff and ecological changes in the source area of the Yellow River for your reference.

Let's take a look at the present situation of drought in the north. Judging from the three indicators used to express the dry and wet conditions in the last five years, namely, precipitation, surface wetness index and drought index, the drought in most parts of the north is very serious, including a considerable number of areas related to the Yellow River. According to the statistics of the National Civil Affairs Bureau, the drought in recent 10 years was very serious, accounting for 50% of the total meteorological disasters. Especially in the last five years, it has increased by 10% compared with the previous10 years. This is the status quo. Looking back, under what background was the drought in the north formed. The change of inland dryness began from 2 million to 3 million years ago, and the dryness suddenly increased, and then it became very large. Scientists also found that this change may be related to the rapid uplift of the Qinghai-Tibet Plateau. Therefore, the drought in the north and the drought in the interior of Asia have been formed for a long time.

Since the Quaternary, the earth's orbital parameters mainly have four periods, which have produced corresponding periodic dry-wet fluctuations and drying trends. The most basic conclusion of our research is that in the Quaternary, the desert in the north expanded in stages, and the arid areas in the north generally became more and more arid. Compared with the last glacial maximum, the southern boundary of the Mu Us Desert moved northward by about 250 km in the last interglacial period. Sporopollen records of nearly 654.38+100000 years explain the history of Holocene vegetation and climate change in Daihai Lake area. Since 2 900, forests have disappeared, vegetation coverage has decreased, and it has entered a cold and dry period.

The main characteristics of paleosalinity and paleotemperature in Daihai Lake reveal the drought trend in recent 3,000 years. The long-term natural background is that in the case of millions to thousands of years, the drought pattern has generally formed in the northern region. What was the situation in 100 recently? In recent 100 years, there are two quasi-periodic changes in dry and wet changes in the north, one is about 20 years, and the other is about 70 years. In recent 50 years, drought and lack of rain in most parts of the north, and rising temperatures have intensified the development of drought, especially in the eastern part of North China and Northwest China, and the boundary of semi-arid areas has expanded to the southeast in an oscillating manner.

The frequency of drought has increased in most parts of the north, and the soil moisture has also decreased, including the source area of the Yellow River, which we are concerned about, which is the situation in the last 50 years.

In the case of zoning, the northwest and east began to suffer from systematic drought in the late 1980 s, and the drought spread eastward and southward in an oscillating manner.

According to the runoff data we used, the runoff of Huayuankou began to decrease in the 1960s, and that of Lanzhou began to decrease in the 1980s.

In 1970s, the runoff in the upper reaches of the Yellow River plummeted, among which the runoff reduction caused by human activities accounted for a considerable proportion.

Let's talk about the future. Our project has established a drought trend prediction system, and put forward the prediction opinions of drought development trend in the future 10~50 years, which have been reported to the relevant state departments.

The work system includes three parts: one is the self-changing law of dry and wet conditions, the other is the main physical factors affecting drought, and the third is the model scenario prediction of regional and global values. About 15 opinions were collected by using the error back propagation neural network, and the preliminary opinions on the prediction of the future 10~50 years were obtained. In our actual forecast, all the factors are quantitative, but considering the credibility of our current forecast level, only some qualitative results are given.

Before 20 10, four regions were predicted, namely northeast, north, south and northwest. There is another project in the northwest and west, so we didn't do that work. From the forecast results, it can be seen that drought will continue in most areas, especially in the southern part of North China, and the eastern part of Northwest China may turn wet. From 20 10 to 2020, most opinions think that it is possible to change from drought to mitigation, but the credibility of this prediction is relatively low because of the contrary opinions. From 2020 to 2050, the eastern part of northwest China may be wet, and the southern part of North China will continue to be dry.

There are also some other predictions, such as 10~50 years, the frequency of extreme drought and flood in northern China will increase, and the frequency of drought in northern and southern North China will increase 10% and 20% respectively; In the next 10~20 years, the measured annual runoff in the upper, middle and lower reaches of the Yellow River will decrease by 10% and 20% respectively. On the basis of climate drought prediction and land use change prediction, a water resource model and a water demand model driven by socio-economic changes are established to predict the relationship between supply and demand of water resources and water shortage in the future. The results show that in the next 50 years, the runoff of Huayuankou will decrease by 5.7% every 10 year, and the whole Yellow River will decrease by 0.43% every 10 year. It is predicted that the annual water shortage in most parts of North China and southeast China will reach10 billion m? 3。 Therefore, it is suggested that under the joint action of global warming and human activities, in the case of serious water shortage in the north in the next 50 years, other river basins must adopt water transfer and non-development water.

In this project, the model of regional environmental system is used to discuss the transition zone of climate ecosystem, that is, the possible climate and environmental benefits of restoring natural vegetation in semi-arid areas. The main feature of this model is the development of a simplified atmospheric environment system model, which can consider the changes of various atmospheric components, including sulfate, aerosol, black carbon aerosol, dust aerosol and so on. And a new hydrological process model is established. The new hydrological model includes two processes: full storage and runoff production, and considers the horizontal heterogeneity of precipitation. In addition, the inversion process of soil moisture is developed, because soil moisture is extremely important to simulate rainfall in arid and semi-arid areas.

In the semi-arid area of Inner Mongolia, through numerical simulation, the changes of soil moisture and precipitation after natural vegetation restoration of 25%, 50% and 75% under different land use patterns were simulated. It can be seen that the restoration of natural vegetation has obvious influence on regional hydrological conditions.

Although this experiment was carried out in the semi-arid area of Inner Mongolia, this method is a numerical simulation experimental method and can also be used in other areas. This model may be a useful tool if we need to understand the possible climate and environmental impacts caused by the restoration of natural vegetation in the source area of the Yellow River.

Academician Ren Jizhou:

Today, many academicians and experts have made incisive and profound exposition on meteorology, hydrology and individual biology. The source of the Yellow River has been deeply studied. I will talk about how to adapt to the current changes in agricultural ecology, especially grassland ecology.

The source of ecological problems at the source of the Yellow River is the climate drought. Everyone agrees, there is no objection. In addition, there are unreasonable human interference. There is nothing we can do about the climate drought, and unreasonable human interference depends on how we use and manage it, which is what we can do.

Characteristics and difficulties of Heyuan management. The source areas of rivers and lakes generally belong to alpine grassland ecosystem, with harsh natural conditions and low ecological productivity. The mode of production is an adaptive mode of production adapted to the alpine grassland ecosystem, and it is the earliest bionics of human beings. The adaptive production mode looks simple, but it actually makes sense. There are also Tibetan living homes, with grassland animal husbandry as the main production and lifestyle. In the core area of Tibetan Buddhist culture, religious culture is systematic and conservative. It is difficult to carry out ecological work in this place. How to govern? The ecological restoration of the source of the Yellow River should seek sustainable development within the framework of comprehensive management of natural ecosystem and social ecosystem, both of which are indispensable. Its specific task is to respect Tibetan traditional culture, rationally organize adaptive production methods, reduce grassland pressure and create a new production and life style of Tibetan society on the basis of ensuring ecological security. This task is very arduous, not only an ecological and natural problem, but also a social problem, so we should unremittingly and gradually form a new way of production and life.

First, what are the strategic measures? First, determine the development direction, focusing on animal husbandry production and ecological security. Establish a perfect ecosystem, including land, biology and society. Why is the rat damage so serious? In recent years, mice have been poisoned. In fact, their natural enemies have also been poisoned, which is very serious. Destroy rats, and you destroy natural enemies. Rats recover quickly, while natural enemies recover slowly. Once I went to Inner Mongolia from Russia via the Mongolian People's Republic, I saw clearly that there were eagles on the Mongolian People's Republic and the grassland was good. When I arrived here, it was bare and all the eagles were gone. Restore a system, not only a plant system, but also the whole system, including animals.