Data: World Water Resources

Water is an important part of natural resources and the main material basis of all biological structures and life activities. On a global scale, water is the link connecting all ecosystems. Natural ecosystems can not only control the flow of water, but also continuously promote the purification and repeated circulation of water. Therefore, water in the natural environment is of decisive significance to the survival of living things and human beings.

Water resources on the earth, in a broad sense, refers to the total amount of water in the hydrosphere.

Seawater is salty water and cannot be directly used, so water resources usually refer to fresh water resources on land, such as rivers, fresh water, lakes, groundwater and glaciers. The freshwater resources on land only account for 2.53% of the total water bodies on the earth, and most of them (nearly 70%) are solid glaciers, that is, alpine glaciers distributed in polar regions and low latitudes, which are still difficult to use. At present, the freshwater resources that are easy to be used by human beings are mainly river water, fresh lake water and shallow groundwater, accounting for about 0.3% of the total freshwater reserves in the world and only 7 ‰ of the total water storage in the world. According to research, from the point of view of water cycle, there are about 9000 cubic meters of fresh water resources that are truly and effectively utilized in the world every year. Saving water resources is what each of us should do! !

Nature and characteristics of water resources

Water and water body are two different concepts. Pure water consists of H2O molecules, while water contains many substances, including suspended solids, aquatic organisms and substrates. Water body actually refers to the natural complex whose surface is covered by water, including rivers, lakes, swamps, reservoirs, glaciers, groundwater and oceans. The relationship between water resources and human beings is very close. Man regards water as the source of life. In the historical development, human beings always gather in places with water for economic activities. With the development of society and the progress of science and technology, human beings are increasingly dependent on water.

Water resources are the most widely distributed and abundant resources in the world. Water covers more than 70% of the earth's surface, totaling 65.438+0.5 billion cubic kilometers; It is also the most fully developed and utilized resource in the world. At present, the annual consumption of water resources by human beings far exceeds any other resources, and the global water consumption reaches 3 trillion tons.

The distribution of water resources on the earth is very uneven, and the precipitation and runoff vary greatly from place to place. About one third of the world's land is short of rain and drought, and other areas are prone to floods in rainy season. For example, in China, the Yangtze River basin and its south area account for more than 82% of the country's water resources, with 36% of cultivated land and little water. In the area north of the Yangtze River, arable land accounts for 64%, and water resources are insufficient 18%, with more land and less water. The Huang-Huai-Hai River Basin, which has the greatest potential for increasing grain production, accounts for 4 1.8% of the whole country, while the water resources are less than 5.7%.

Present situation of water resources utilization

Although the total amount of water resources in China is large, the per capita amount is not rich. The characteristics of water resources are uneven regional distribution and uneven combination of water and soil resources; The distribution is concentrated during the year, with great interannual changes; The years of continuous abundant water and continuous drought are more prominent; River sediment deposition is serious. These characteristics make China prone to floods and droughts, and the contradiction between supply and demand of water resources is prominent, which also determines the arduous task of water resources development and utilization and river regulation in China.

1. contradiction between water resources utilization and supply and demand

The average annual runoff of surface water in China is about 2.7 trillion cubic meters, which is equivalent to 5.5% of the global total land runoff, ranking fifth in the world, lower than Brazil, the former Soviet Union, Canada and the United States. China also has glaciers with an annual melting water of nearly 50 billion cubic meters, about 800 billion cubic meters of groundwater and nearly 5 million cubic kilometers of offshore seawater. At present, China's available water resources are about 1. 1 trillion cubic meters per year, while in 1.980, China's actual total water consumption has reached 507.5 billion cubic meters, accounting for 46% of the available water resources.

Since the establishment of People's Republic of China (PRC), a lot of work has been done in water resources development and utilization, river regulation and water disaster prevention, and great achievements have been made.

In terms of urban water supply, at present, more than 300 cities across the country have built water supply systems, with the daily supply of tap water reaching 40 million tons and the annual supply exceeding 654.38+000 billion cubic meters; The daily water supply capacity of self-provided water sources in urban industrial and mining enterprises and institutions totals more than 60 million tons, and the annual water supply is 654.38+07 billion cubic meters; Of the more than 7,400 towns, 28% have established water supply facilities, with a daily water supply capacity of about 8 million tons and an annual water supply of 2.9 billion cubic meters.

In terms of farmland irrigation, China's existing farmland irrigation area is nearly 720 million mu, and farmland with irrigation facilities accounts for 48% of the country's cultivated land, but its grain production accounts for 74% of the country's total grain output.

In flood control, there are more than 200,000 kilometers of dikes, protecting 500 million mu of cultivated land and more than 0/00 large and medium-sized cities. At present, there are more than 80,000 large, medium and small reservoirs with a total storage capacity of more than 440 billion cubic meters, and the control basin area is about 65.438+0.5 million square kilometers.

Hydropower, the installed capacity of hydropower in China is nearly 30 million kilowatts, accounting for about 29% of the total installed capacity and 20% of the power generation.

However, with the rapid development of industry and cities, the demand for water is increasing and there is a shortage of water supply. According to the statistics of 1984 and 196 water-deficient cities, the daily water shortage reaches140,000 cubic meters, and the degree of water resources security has become the main constraint factor for economic development in some areas.

The contradiction between supply and demand of water resources is not only influenced by natural factors such as quantity, quality, distribution and development conditions of water resources, but also restricted by social and economic factors of water resources demand of various departments.

The total amount of water resources in China is not small, but the per capita water resources are very poor, which is only 1/4 of the world's per capita value (China's per capita surface water resources are about 2,700 cubic meters, ranking 88th in the world). Compared with China, Canada is 48 times, Brazil is 16 times, Indonesia is 9 times, the former Soviet Union is 7 times, and the United States is 5 times, which is also lower than Japan, Mexico, France, the former Yugoslavia, Australia and other countries.

There are many water resources in the south and few in the north of China, and the regional distribution is quite different. The annual runoff of the Yellow River basin only accounts for about 2% of the national annual runoff, which is about 6% of the Yangtze River. In the total annual runoff of China, the Huaihe River, Haihe River, Luanhe River and Liaohe River only account for about 2%, 1% and 0.6% respectively. The per capita water consumption of the Yellow River, Huaihe River, Hailuan River and Liaohe River is only 26%, 15%,1.5% and 2 1% of the per capita value of China respectively.

With the growth of population and the continuous development of industrial and agricultural production, the contradiction between supply and demand of water resources is increasing. From the beginning of this century to the mid-1970s, the world's agricultural water consumption increased by 7 times, and the industrial water consumption increased by 2 1 time. China's water consumption has also increased rapidly. By the end of 1970s, China's total water consumption was 470 billion cubic meters, 4.7 times that of the early days of the People's Republic of China. Among them, urban domestic water consumption increased by 8 times and industrial water consumption (including thermal power) increased by 22 times. At the end of 1970s, Beijing's urban water consumption and industrial water consumption were more than 40 times that of the early days of the People's Republic of China. By the end of 1970s, urban water consumption in Hebei, Henan, Shandong, Anhui and other provinces had increased dozens of times, and some even exceeded 100 times. Therefore, the contradiction between supply and demand of water resources is extremely prominent.

Due to the increasingly acute contradiction between supply and demand of water resources, it has produced many adverse effects. First of all, it has a great impact on industrial and agricultural production. For example, 198 1 year, Dalian lost 600 million yuan of industrial output value due to water shortage. Among the 654.38+0.5 billion mu of cultivated land in China, there are still 830 million mu of dry land without irrigation facilities, and another 654.38+0.4 billion mu of water-deficient grassland. Every year, 300 million mu of farmland in China suffers from drought. There are still 40 million people and 30 million livestock in the northwest agricultural and pastoral areas with difficulty in drinking water. Secondly, it brings inconvenience to people's life and work. Water supply for buildings in some cities is insufficient or often cut off. Some water-deficient cities have to take regular water supply rationing, which makes people's lives difficult. Third, over-exploitation of groundwater leads to the continuous decline of groundwater level and the depletion of water resources. In 24 of the 27 major cities, underground water drop funnels have appeared.

2. Water conservancy construction and flood disaster

Due to the influence of geographical location and climate, China is a country with frequent floods and droughts, especially floods, which have long plagued economic development. According to statistics, from 206 BC to 2 155 BC, * * had 1062 floods, once every two years on average. For more than two thousand years, the Yellow River burst twice every three years and changed its course once every hundred years. A flood in 1887 alone killed 930,000 people, and the national flood in 193 1 year lost 3.7 million people. After the founding of People's Republic of China (PRC), floods continued, resulting in huge losses. Therefore, building water conservancy projects, regulating rivers and preventing floods are actually major plans for the country to govern the country and maintain peace, and are also very important strategic tasks.

In the past 40 years, China has repaired more than 200,000 kilometers of riverbanks and protected 500 million mu of cultivated land. More than 80,000 reservoirs, 2.63 million electromechanical wells and more than 66 million kilowatts of irrigation and drainage machinery have been built. The electromechanical irrigation and drainage area is 460 million mu, the waterlogging area is about 290 million mu, the saline-alkali land area is 72 million mu, and the soil erosion control area is 5 1 10,000 square kilometers. These water conservancy projects not only provide 500 billion cubic meters of water for agriculture, industry and urban life every year, but also solve the drinking water problem of 654.38+23 million people and 73 million livestock in mountainous and pastoral areas. But also played a great role in flood control.

With the rapid increase of population and unreasonable utilization of water and soil resources, the water environment has deteriorated and floods have intensified. Especially since the summer of 199 1, there have been persistent rainstorms or heavy rainstorms in the Jianghuai, Taihu and other areas of the Yangtze River basin in China, and some areas have experienced floods once in a century. As of August 1, the number of victims reached 220 million, with more than 50,000 casualties, 29 1 10,000 houses collapsed and 6.05 million houses were damaged. The affected area of crops is about 310.50 billion mu, and the disaster area is10.90 billion mu, with direct economic losses as high as 68.5 billion yuan. In the face of this large-scale serious flood disaster, we should further improve our understanding of the serious threat of flood disaster, sum up experiences and lessons, and find prevention and control countermeasures.

In addition to natural factors, the main causes of flood disasters are:

(1) Unreasonable utilization of natural resources. In particular, deforestation destroys the balance of water and soil and worsens the ecological environment. As mentioned earlier, soil erosion is serious in China. Although it has controlled 5 1 10,000 square kilometers since the founding of the People's Republic of China, the current soil erosion area has reached10.6 million square kilometers, with 5 billion tons of sediment lost every year, and about 3.5 billion tons of sediment are taken away by rivers, reservoirs and lakes, including10.20 billion tons. Unreasonable reclamation and the reduction of lake area have reduced the flood control capacity of lakes. According to the investigation of Nanjing Institute of Geography and Lakes of Chinese Academy of Sciences, at the end of 1970s, there were more than 2,300 lakes in China, with an area of 1 km2 and a total area of 7 1 km2, accounting for 0.8% of the total land area. Lake water resources are 707.7 billion cubic meters, of which fresh water is 225 billion cubic meters, accounting for 8% of the total land water resources in China. Over the past 30 years since the founding of the People's Republic of China, the number of lakes in China has decreased by more than 500, covering an area of about 65.438+0.86 million square kilometers, accounting for 26.3% of the existing lake area, and the water storage capacity of lakes has decreased by 565.438+0.3 billion cubic meters. The water system and natural water surface in the middle and lower reaches of the Yangtze River have decreased. Since 1954, the water surface of lakes in Hubei, Anhui, Jiangsu, Dongting and Poyang Lake has decreased by about 12000 square kilometers, and the flood control and waterlogging resistance have been greatly weakened. On the other hand, the river siltation is occupied and the flood discharge capacity is reduced. Because a large amount of sediment is deposited in the river, the riverbed of many rivers is raised, which reduces the flood discharge capacity and increases the probability of flood. For example, the flood discharge capacity of the Huaihe River has dropped by 3000 cubic meters per second. In addition, the crowded river channel narrows the cross section of water, reduces the ability of flood discharge and regulation, and increases the degree of flood damage.

(2) The flood control standard of water conservancy projects is low. Flood control standards of major rivers in China are generally low. At present, except for the lower reaches of the Yellow River, the other six rivers such as the Yangtze River and Huaihe River can only flood once every 60 years 10 ~ 20 years. Many large and medium-sized cities have poor flood control and drainage facilities and are often threatened by major floods. The middle and lower reaches of major rivers threatened by floods cover an area of 738,000 square kilometers, accounting for 7.7% of the total land area, including 500 million mu of cultivated land and a population of 420 million, all accounting for more than13 of the country, and the total industrial and agricultural output value accounts for about 60% of the country. In addition, the drainage standard of the vast rural areas in the middle and lower reaches of the river is lower, which is far from meeting the current requirements of flood control and drainage with the development of rural economy.

(3) Population growth and economic development have deepened the disaster. On the one hand, the ability to resist floods is weakened, on the other hand, due to social and economic development, the degree of disaster has greatly increased. After the founding of People's Republic of China (PRC), the population has more than doubled, especially in the eastern region. The population density in the Yangtze River Delta is 10 times of the national average. The total industrial and agricultural output value of China was only 46.6 billion yuan in 1949, and reached 2,408.9 billion yuan in 1988, an increase of 5 1 times. 10 years, township enterprises have developed rapidly. The output value of township enterprises in the eastern and central regions accounts for 98% of the total output value of township enterprises in China. Due to the continuous development of economy, all kinds of losses caused by floods with the same frequency have multiplied. For example, 199 1 year, the rainfall in Taihu Lake Basin from May to July is 600-900 mm, which is not seen for 50 years. There is no flood exceeding 1954, but the disasters and economic losses caused are much more serious than that in 1954. In addition, agriculture in the middle and lower reaches of the river is generally developed, and there are many commodity grain, cotton and oil production bases. Once affected, agricultural losses are also quite serious.

3. Water pollution and its harm

Water is the most important natural solvent, so it is easy to be polluted. Common water pollution has the following categories.

(1) Eutrophication of water body Eutrophication of water body is a kind of organic pollution, which makes the water quality worse because too many nutrients such as nitrogen and phosphorus enter the natural water body. About half of the fertilizers commonly used in farmland are unused and flow into groundwater or ponds and lakes, and a large amount of domestic sewage often makes the water body too fat. Excessive nutrients promote the reproduction of phytoplankton in waters, such as cyanobacteria, diatoms and aquatic plants. Sometimes the whole water surface is covered with algae to form a "splash", which is deposited at the bottom of the water after algae die, and microbial decomposition consumes a lot of dissolved oxygen, resulting in a large number of fish deaths due to lack of oxygen. Eutrophication of water will accelerate the decline of lakes and make them develop into swamps.

Eutrophication in the coastal waters of the ocean leads to a large number of dinoflagellates (such as gymnoctiluca and noctiluca scintillans) breeding together, making the seawater pink or reddish brown, which is called red tide, which is very harmful to fisheries. In recent years, it has occurred many times in the northern Bohai Sea and the South China Sea.

(2) Toxic substances include two types: one refers to heavy metals such as mercury, cadmium, aluminum, copper, lead and zinc; The other is organic chlorine, organophosphorus, polychlorinated biphenyls, aromatic amino compounds and other chemical products. Many enzymes rely on the complexation between protein and metal ions, so some trace elements (such as manganese, boron, zinc, copper, molybdenum, cobalt, etc. ) is required. However, unwanted metals, such as mercury and lead, and even excessive essential trace elements, such as zinc and copper, can upset the balance between protein and metal ions, thus weakening or terminating the activity of some protein. For example, mercury and lead have a strong tendency to combine with some enzymes in the central nervous system, which can easily lead to insanity, such as madness, mental retardation, coma and even death. In addition, mercury forms a specific combination with protein and interacts with the genetic material DNA, which is also the reason why mercury poisoning often leads to serious birth defects.

The combination of these heavy metals with protein will not only lead to poisoning, but also lead to biological accumulation. After binding with protein, heavy metal atoms cannot be excreted, and gradually accumulate from low dose to high concentration, thus causing harm. A typical example is the aforementioned Minamata disease in Japan. After investigation, it is found that the toxicity of metallic mercury is not great, and most mercury can pass through the digestive tract without being absorbed. Mercury is absorbed by bacteria in water sediments, which makes mercury react chemically. In the reaction, mercury and methyl combine to form organic compound of methylmercury (Hg-CH3), which is different from mercury itself. The absorption rate of methylmercury is almost equal to 65,438+000%, its toxicity is almost 65,438+000 times greater than that of metallic mercury, and it is not easy to excrete.

Organochlorine (or chlorinated hydrocarbon) is an organic compound in which one or several hydrogen atoms are replaced by chlorine atoms. This compound is widely used in plastics, electrical insulators, pesticides, fire extinguishing agents, wood preservatives and other products. Organochlorine has two characteristics that are particularly easy to bioaccumulate, namely extremely stable chemical properties, high fat solubility and low water solubility. The stability of chemical properties shows that it is not easy to decompose in the environment and cannot be metabolized by organisms. High fat solubility means that it is easily absorbed by organisms and cannot be excreted once it enters, because excretion needs water solubility, resulting in biological accumulation and poisoning. Typical organochlorine pesticides, such as DDT and bhc, have been banned in many countries because of their serious harm to biology and human body.

(3) Thermal pollution Many waste heat generated in industrial production processes is discharged into the environment, which will raise the environmental temperature to an unsatisfactory or biologically unsuitable level, which is called thermal pollution. For example, in the process of steam recondensation, 2/3 of the heat released by power plant fuel is emitted to the surrounding environment. The most common heat dissipation method is to pump the water out of rivers and lakes, pour it on the cooling pipe, and then send the heated water back to the natural water body. The water passing through the cooling system itself is hot enough to kill most living things. Experiments show that small changes in water temperature have a profound impact on the ecosystem.

(4) Marine Pollution With the rapid increase of population and the development of production, China's marine environment has been polluted and destroyed to varying degrees.

According to the investigation of 1980, there are 6.65 billion tons of industrial and domestic sewage directly discharged into the offshore every year, and the toxic and harmful substances discharged with these sewage every year are oil, mercury, cadmium, lead, arsenic, aluminum and cyanide. About a quarter of the pesticides used in coastal counties of China flow into the sea every year, about 50,000 tons. These pollutants are very harmful, and the pollution in the Yangtze River estuary and Hangzhou Bay is becoming more and more serious, which has begun to endanger Zhoushan Islands, the largest fishing ground in China.

Marine pollution leads to the death of fish in some sea areas, the decrease of biological species, the increase of toxic residues in aquatic products, the migration of fishing grounds and the abandonment of many beach farms. Such as JIAOZHOU bay 65438 ~ 1964 intertidal marine life 17 1 species; 1974 ~ 1975 decreased to 30 species; There were only 17 species in the early 1980s. The maximum annual output of whitebait in the Bailang Estuary of Laizhou Bay is 300,000 Jin, which is about 65,438+100,000 Jin in 1963. Now it has basically stopped production.

Protection and rational utilization of water resources

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1. Strengthen water resources management and establish water-saving economy.

The key to alleviate the shortage of water resources in China lies in improving water use efficiency and establishing water-saving economy. The main sign of water-saving economy should be to develop industries with good quality, high output value, less water consumption and less pollution discharge, and form a reasonable industrial structure; Industrial layout should adapt to water resources conditions; It is necessary to improve the efficiency of agricultural water use and develop crops with less water consumption; It is necessary to make the water quota and drainage quota of industrial and agricultural products reach the advanced level at home and abroad; Popularize advanced household water-saving equipment; Strengthen the reuse of water for many times and develop sewage resources. Doing a good job in industrial water saving not only reduces the newly added water, but also naturally reduces the amount of industrial wastewater. Industrial water-saving indicators are usually expressed by the reuse rate of water, and the reuse rate of industrial water in China is low. In the early 1980s, the national average was only about 20%, and only a few cities reached 40%. China's agricultural water consumption accounts for 88% of the country's water intake, which is far from the United States (49%), the former Soviet Union (59%), Japan (46%) and France (47%), and it is extremely disproportionate to the requirements of modern national economic development. In the future, we should improve the efficiency of irrigation water, develop agricultural irrigation with organic sewage that meets the water quality standards, and cultivate and popularize drought-tolerant crops in order to achieve stable and high yield.

2. Establish a sewage treatment system

With the treatment and control of industrial waste, the pollution of heavy metals to water will be reduced, and the treatment of organic sewage will become more and more prominent, which is more important in cities.

The use of sewage treatment plants is the main way to treat organic sewage in industrialized countries. In the United States, Britain, France, Germany, etc. There is a sewage treatment plant for every1~10.5 million people on average. But these plants can only solve biodegradable organic matter, but can't remove nitrogen, phosphorus and non-biodegradable organic matter. In recent years, more and more countries have turned to the development of ancient natural purification methods such as land treatment and biological ponds (oxidation ponds) to purify organic sewage by using ecosystems. For example, the ecological project in Marquis Root, Michigan, USA consists of water storage ponds, aerated pond and irrigation fields, while Williby Ranch in Victoria, Australia adopts a treatment system consisting of oxidation ponds, farmland and pasture. Reclaimed water is obtained by recycling sewage through environmental ecological engineering to expand water supply, which can alleviate the shortage of water resources in some areas to some extent.

3. Development and utilization of sky water resources

Sky water (that is, the water content in the air) is only 28 trillion tons, accounting for only 0.002% of the total water in the world, but it plays an important role in weather changes. 95% of the water in the sky is steam, and clouds and precipitation clouds only account for 5%. Although the total amount of water in the sky is small, it circulates quickly, with a cycle of only 8.7 days, while the cycle of groundwater and surface water is 400 years. That is to say, the sky water can be circulated 42 times a year, and the annual sky water volume is 1 176 billion tons, far exceeding the total surface water.

The development and utilization of sky water resources is to investigate the situation of sky water resources in this area, including the temporal and spatial distribution of sky water vapor, clouds, rain and snow, climate characteristics and variability, and the availability of sky water resources. Secondly, artificial precipitation enhancement is carried out in water-deficient areas. The experimental results of more than 40 years in the world show that under suitable cloud conditions, the average artificial precipitation can reach 10 ~ 30% by using the correct catalytic method. Many tests have been carried out in China since 1958. The test results of Gutian Reservoir 1975 ~ 1986 in Fujian Province show that the average precipitation increases by 23.8%, and the investment-benefit ratio calculated by power generation alone reaches 1∶50.

4. Main countermeasures for flood control and disaster reduction

Flood disaster is a natural social phenomenon, which is caused by both natural factors and human activities. As a natural disaster, it is impossible to completely avoid it. However, with the progress of science and technology and the enhancement of economic strength, people's understanding of the law and evolution of disasters will continue to improve and deepen. Through pre-disaster prediction, early warning and taking prevention and control measures, the losses caused by disasters can be reduced to some extent. Therefore, the prevention and control of flood disasters should be regarded as the central task of national land consolidation and the important content of social and economic development planning, and the national medium-and long-term flood control master plan should be formulated and implemented through legislation. At the same time, it is necessary to formulate flood control laws and regulations, control water according to law, and emphasize unified management. Accelerate the research work of flood disaster prediction, early warning and disaster assessment. The industrial layout should adapt to the change of water environment, and through various measures such as soil and water conservation, water storage project, dam construction, river dredging, irrigation and drainage, and the establishment of flood storage and detention areas, the water environment will be transformed into a favorable direction, and obvious ecological and social benefits will be achieved. The Three Gorges Project in China is a major project focusing on flood control and power generation. If it can be successfully built, it will play a great role in flood control and disaster reduction and economic construction.

The Present Situation of Saving Water Resources in China

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China is a country short of water resources, and the total amount of water resources ranks sixth in the world. In terms of per capita water resources, the per capita possession is 2500 cubic meters, accounting for 1/4 of the world's per capita water, ranking 1 10 in the world, and being listed as one of the 13 water-poor countries by the United Nations. At present, more than 400 of the 668 cities in China are short of water, and the annual water shortage exceeds 6 billion cubic meters. For a long time, influenced by the traditional value concept of "inexhaustible water resources", water resources have been used for a long time without compensation, which leads to people's low awareness of saving water and leads to huge waste and unsustainable development and utilization of water resources. The shortage of water resources is increasing day by day. Rational development and utilization of water resources, protection of ecological environment and maintenance of harmony between man and nature have become the common mission of mankind in the 2 1 century.

The water crisis will lead to further deterioration of the ecological environment. In order to obtain enough water resources for the society, we must increase the development of water resources. Overexploitation of water resources may lead to a series of ecological and environmental problems. The seriousness of water pollution is not only the result of over-exploitation of water resources, but also the reason for further strengthening the development of water resources. They interact with each other and form a vicious circle. It is generally believed that when the runoff utilization rate exceeds 20%, it has a great impact on the water environment, and when it exceeds 50%, the impact is serious. At present, the utilization rate of water resources in China has reached 19%, which is nearly three times the world average, and even higher in some areas. Such as 1995, the development and utilization rates of Songhua River, Haihe River, Yellow River and Huaihe River reach over 50%, among which the Huaihe River Basin reaches 98%. In addition, over-exploitation of groundwater will cause land subsidence, seawater intrusion, seawater intrusion and other environmental problems.

First, the present situation of water saving in China

In terms of domestic water saving, at present, all cities and most towns in China have basically realized the paid installation of metering water meters, and basically canceled the household water package system.

In terms of industrial water saving, the current national water reuse rate has generally increased by more than 40% compared with the early 1980s, and the water consumption per 10,000 yuan of output value has decreased by 50% compared with the 1980s. From 1983 to 1995, the cumulative water saving was nearly 20 billion cubic meters, the sewage discharge was reduced by nearly/kloc-0.5 billion cubic meters, and the seawater utilization in coastal cities was nearly 6.5 billion cubic meters.

In terms of agricultural water use, in recent years, China has built 300 key counties to save water and increase production and 209 high-standard demonstration areas to save water and increase efficiency. Focusing on water-saving irrigation, 99 large-scale irrigation areas and 40 medium-sized irrigation areas have been continuously built and renovated, and a number of national-level demonstration areas have been built. By the end of 1998, the area of water-saving irrigation projects in China reached 228.5 million mu, including 26 million mu of sprinkler irrigation, drip irrigation and micro-sprinkler irrigation. In addition, the promotion of non-engineering measures saved 224 million mu of water.

Second, the problems of water saving in China

1, lack of understanding. Water saving is a wide social and regional work. Doing a good job in water saving needs social understanding and support, especially alleviating regional water shortage and water environment problems such as water shortage in North China and the lower reaches of the Yellow River, and requires the joint efforts of all members of society in all regions (or basins), regions, departments and industries to achieve results. However, people's understanding of water saving in China is generally not high, and water saving often stays in words.

2. Insufficient investment. Water-saving work has a wide range, a large quantity and a complex situation, which requires a lot of investment and certain advanced technology. For example, industrial water can generally be divided into cooling water, boiler water, washing water and process water, in which the saving of cooling water is relatively easy, while the saving of washing water and process water is relatively difficult. However, no matter what kind of industrial water is used, it is necessary to update and transform water equipment, and some even need to update and transform process equipment. This requires a lot of investment. With the increase of water-saving efforts and the improvement of water reuse rate, the investment in unilateral water-saving will be larger and larger, and the technical requirements will be higher and higher. At present, there is no fixed investment channel for top-down industrial water saving in China, and water saving projects are generally for one. In recent years, the investment in agricultural water saving has been strengthened, but the intensity is not enough. Insufficient investment and backward technology have widened the gap between China's industrial and agricultural water consumption level and the international level.

3. The mechanism is weak. At present, there is not a set of operation mode for water-saving work to adapt to the market economy. Low water price is the main reason. The direct economic benefits of many water-saving projects are limited, mainly reflected in social and ecological benefits, alleviating the contradiction between supply and demand of water resources, while the state lacks preferential development policies. For these reasons, many water users are not enthusiastic about water saving, water saving has not really become the spontaneous action of enterprises and farmers, and water saving work is in a passive state.

4. The legal system is not strong. Water saving involves all walks of life and thousands of households. Without the promotion of the market, the power to save water will inevitably be insufficient. Only relying on the market to promote, without government guidance, water saving is bound to be difficult to see results. To do a good job in water saving, we must fully consider the characteristics of water saving work, relying on market promotion and strengthening government behavior. Only by combining the strong promotion of the government with the active and conscious actions of practical and effective water users can China's water-saving work be promoted to a new level.