What are the characteristics of water resources in China reflected by the drought in the north? urgent ....

Drought characteristics and defense in China

Most of China is located in the East Asian monsoon region, with complicated weather and climate. It is one of the regions with fragile climate in the world and one of the countries most seriously affected by meteorological disasters. Meteorological disasters in China are characterized by many types, wide distribution, high frequency, long duration, serious secondary disasters, great economic losses and many casualties.

Drought is the most common climate disaster in China, which has the greatest impact on agricultural production. The drought-affected area accounts for more than half of the total affected area of crops, and the proportion of severe drought years is as high as 75%. According to incomplete statistics, from 206 BC to 2 155 BC, there were 1056 droughts in China, once every two years on average, such as the drought in Shaanxi 1928 to 1929, which killed 9.4 million people in China. After the founding of New China, the state invested heavily in building water conservancy facilities and expanding irrigation area, which greatly improved agricultural production conditions and enhanced the ability to defend against drought disasters. However, restricted by climatic conditions, with the development of social economy, the growth of population, the sharp increase of water consumption in agriculture, industry and cities, the deterioration of water environment and the decrease of available water, the frequency of drought in China is still very high, the affected area is large, and drought disasters are increasing. According to statistics, in the past 50 years, the average drought-stricken area in China has reached 2210.7 million hectares. In 1990s, with the intensification of global warming, droughts occurred frequently in northern China, with the average annual drought-affected area rising to 27 1, 1, and the severely drought-affected areas in 2000 and 2006 reached 40,544 and 38,470,000 hectares, respectively, and 5438+0.

First, the distribution characteristics of drought in China

Temporal and spatial distribution characteristics of 1.

In our country, drought can happen all the year round. Spring drought mainly occurs in the Huanghuai River Basin and its northern area, and the probability of spring drought in North China is about 70%, which is called "Nine Spring Droughts in Ten Years". In some years, the spring drought can last until June and July, resulting in continuous drought in spring and summer, which has a serious impact on agricultural production, such as 1962, 1972, 1997, etc. 1965 and even the continuous drought in spring, summer and autumn have a more serious impact on agricultural production.

Summer drought is usually divided into early summer drought and summer drought. Drought mainly occurs in the north in early summer. Summer drought is a drought during the "dog days" in midsummer, which mostly occurs in the south of Qinling Mountains and Huaihe River to the north of South China, especially in the middle and lower reaches of the Yangtze River. Generally, the impact of summer drought is not very serious, and the damage is more serious only when the drought lasts until September 10 or June 1 10, that is, summer and autumn drought.

Autumn drought mostly occurs in central and southern China, which has a great influence on the growth of late rice in southern China. Autumn drought in the north has little effect on crops, but it will be unfavorable to the emergence of winter wheat.

Winter drought mainly occurs in South China and the eastern part of Southwest China. Because there are crops growing here in winter, there is more water demand, and winter drought will occur in years with less rain. In some years, the drought lasts for a long time, and the winter drought can last until early spring of the following year. For example, from June 200419981April 1999 and June 2004+10 to April 2005, continuous droughts occurred in parts of southern China, which had a great impact on industry, agriculture and domestic water. Drought in southwest China can last for 4 ~ 5 months, and sometimes occurs in autumn, winter and spring. Such as 1959, 165438+ 10 to 1960, which lasted for 7 months.

Affected by the interannual and periodic fluctuations of precipitation, the occurrence of drought also changes periodically. Since 195 1 year, the drought-affected area in China has been on the rise, and it has changed greatly year by year. In 1950s and 1960s, the drought-affected area was small; The drought-affected area in the 1970s increased by nearly 1 times compared with the previous two decades. The area affected by drought decreased slightly in 1980s, but it has increased obviously since 1990s. In the past 50 years, there were 13 years in which the drought area exceeded 30 million hectares, including 6 years since the 1990s. Generally speaking, there are three low-value periods and four high-value periods in drought-stricken areas in China. 195 1 ~ 1957, 1963 ~ 1970, 1982 ~ 1984, and the drought-affected area is generally below 20 million hectares every year. 1959 ~ 196 1 year,1971~1981year,1986 ~/kloc-.

2. Five major drought centers in China

Drought may occur in all parts of China, but the frequency and degree are different. According to the statistics of the past 50 years, there are five obvious drought centers in China:

(1) Northeast arid area. The drought in this area mainly occurs from April to August in spring and summer, with a probability of 66% in spring and 50% in summer.

(2) Huang-Huai-Hai arid area (northwest east and north China). This area is the largest arid area in China with less precipitation and great changes, and the number of droughts also ranks first in the country. Drought may occur in March 3- 10/0 during the crop growth period, and there will be persistent drought in spring, summer and autumn in some areas in a few years, but spring drought is the main one, and spring drought occurs to varying degrees almost every year.

(3) the Yangtze river basin area. From March to 1 1 month, drought can occur in this area, but it is mainly concentrated in summer and autumn. From July to September, drought opportunities are the most, and summer drought is the most harmful.

(4) South China. Drought can occur all year round in this area, but due to the early rainy season in South China, typhoon precipitation often occurs in summer and autumn, so drought mainly occurs in late autumn, winter and early spring. In most years, the drought lasts for 3-4 months, and the longest is 7-8 months.

(5) Southwest China. The drought in this area is relatively small. Generally, the drought starts from June 10 or June10 of the previous year, and lasts until June of April or May of the following year. However, drought mainly occurs in winter and spring.

Two. The effects of drought

Drought is a kind of climate disaster, which is one of the important factors restricting sustainable economic development and social security, and affects all aspects of human social and economic activities. Drought leads to soil water shortage, which affects the normal growth and development of crops and reduces production; Secondly, water resources are insufficient, drinking water for people and livestock is difficult, urban water supply is tight, and urban development is restricted; Long-term drought will also lead to the deterioration of the ecological environment. Drought can be divided into soil drought and atmospheric drought, and if both occur at the same time, the harm is more serious.

Drought is one of the most important natural disasters in China, and every drought in history has brought profound disasters to the Chinese nation. In the last hundred years, 1900, 1928 ~ 1929, 1934,1956 ~196/,/kloc-0. A continuous drought occurred in 1959 ~ 196 1 year, and disasters affected 10 ~ 15 provinces (autonomous regions and municipalities), with an average drought-affected area of 36.59 million hectares, resulting in disasters15.33 million hectares.

Drought has caused more and more losses to national economic construction and people's lives and property, seriously affecting social security, national economic development and people's living environment. With the development of economy and the growth of population, the absolute value of losses caused by drought has obviously increased. In 2000, there was a nationwide drought in China, especially in spring and summer from February to July in the north of the Yangtze River. The drought affected a wide range, lasted a long time and caused serious disasters. The drought period in North China and the eastern part of Northwest China lasted for half a year. In 2000, the drought-affected area in China was as high as 40.54 million hectares, the highest since the founding of the People's Republic of China, of which 8 million hectares were not harvested, and nearly 60 billion kilograms of grain and 565.438 billion yuan of cash crops were lost due to drought, affecting more than 65.438+0.959 ~ 65.438+0.961year.

Drought and water shortage have seriously restricted the development of rural economy. Drought and water shortage make it difficult for millions of people to drink water every year. From February to May in 20001year, the severe drought in northern China not only caused drought to more than 22 million hectares of farmland, but also caused temporary drinking water difficulties for 6,543,800 people and 6,543,800 large livestock.

Drought, especially years of drought, not only brings the most obvious and direct harm to agricultural production, but also causes crop failure, which has a far-reaching adverse impact on water resources, ecological environment and economic and social development. The Yellow River has been cut off frequently since 1970s, and the most serious drought occurred in 1997. Due to the severe drought, Lijin Hydrological Station in the lower Yellow River was cut off for 226 days, with the longest cut-off reach exceeding 700 kilometers. The interruption of the Yellow River has seriously affected people's life, industrial and agricultural production and ecological environment in the basin. The lack of water resources and the serious shortage of industrial production and domestic water have led to the deterioration of ecological environment, desertification and salinization of land, further leading to the intensification of sandstorm activities, the continuous decline of forest coverage and the increasingly serious grassland degradation. Due to the lack of water resources, over-exploitation of groundwater also leads to land subsidence.

Three. A severe drought in recent 10 years

1992 severe summer drought in Huang-Huai-Hai region. From mid-May to early July, 1992, most areas in Huanghuai sea area continued to lack rain, and the total precipitation was generally only 20-50 mm, which was 50-80% less than normal. The lower reaches of the Yellow River and Huaihe River were once cut off. Severe summer drought occurred in Shandong, Henan, Hebei, Shanxi, northern Jiangsu, northern Anhui and other places, and the drought-affected area reached more than130,000 hectares.

1994 severe summer drought in jianghuai and Sichuan basins. 1994 The precipitation in Jianghuai area from late June to mid-August is only/kloc-0 ~ 200 mm, while the precipitation in most areas of Sichuan Basin and southern Shaanxi, Guanzhong, Longdong and Longnan from mid-July to mid-August is only 50 ~ 100mm, which is 5 ~ 80% less than normal, resulting in different degrees of drought. Among them, the drought in Anhui and Jiangsu provinces is the heaviest since the founding of the People's Republic of China, and the drought in Shaanxi, Sichuan, Henan and other provinces is also one of the serious years.

1997 severe summer drought in northern China. 1in the summer of 997, there was continuous low rainfall and high temperature weather in most parts of northern China. The precipitation is generally150 ~ 300mm, which is 20 ~ 40% less. Among them, parts of North China and Northwest China are less than 50% to 70%, and the drought-affected area is more than 20 million hectares, including more than 9 million hectares of severe drought, which is rare since the founding of the People's Republic of China.

In 2000, a large area of drought occurred in spring and summer in the north. From February to July, 2000, the precipitation in most areas north of the Yangtze River was obviously less than normal, and the temperature was higher than normal, which led to frequent sandstorms and large-scale spring drought. After the summer, there is still little rain in most parts of North China and the eastern part of Northwest China. Coupled with the continuous high temperature, there is drought in spring and summer. In 2000, the drought affected a wide range, lasted a long time and caused serious disasters. Jilin, Heilongjiang, Liaoning, Inner Mongolia, Shanxi, Hebei, Tianjin, Shandong, Gansu, Shaanxi, Anhui, Hubei, Ningxia and other provinces and cities have suffered from extensive drought. This year, the drought-stricken area in China reached 40.54 million hectares, the highest since the founding of the People's Republic of China.

200 1 spring and summer drought in the north. From February to early June, 2006,5438+0, the precipitation in most areas north of the Yangtze River was unusually low, the temperature was generally high, the evaporation was large, the farmland lost water quickly, and a large-scale continuous drought occurred, especially in Shanxi, Shandong, Henan, Liaoning, Hebei and other provinces. This is another severe drought in northern China after 1997, 1999 and 2000. Due to years of drought and lack of rain, water storage in water conservancy projects is insufficient, groundwater can not be replenished obviously, and the shortage of water resources is becoming increasingly serious.

In 2004, severe autumn drought occurred in southern China and the middle and lower reaches of the Yangtze River. After the autumn of 2004, the precipitation in most parts of the south continued to be less. From September to June, the average precipitation in Guangdong, Guangxi, Hainan, Hunan, Jiangxi, Anhui, Jiangsu and other provinces (regions) was only 98 mm, the lowest since 195 1. At the beginning of June 1 1, the arid area almost extended to the whole middle and lower reaches of the Yangtze River and South China, among which Guangxi, most of Guangdong, Hainan, southwestern Fujian, southern Hunan, eastern Hubei, most of Jiangxi, central and southern Jiangsu and Anhui, northern Zhejiang and other places reached the standard of severe drought, and some areas reached the standard of severe drought, with the drought-affected area of crops reaching more than 565,438 hectares and 900 hectares.

Four. Drought prevention and countermeasures

Optimize agricultural structure according to drought law. Agriculture is the most sensitive and directly affected by drought. Reasonable arrangement of the industrial structure of agriculture and animal husbandry can make use of limited resources and achieve a double harvest of economic and ecological benefits. In areas with annual precipitation below 400 ~ 500mm, animal husbandry is dominant, supplemented by agriculture and forestry. For example, in areas with annual precipitation above 550 mm, it is necessary to rationally select crop varieties, adjust crop planting structure, and seek advantages and avoid disadvantages.

Improve the utilization rate of water resources. Rational irrigation, scientific water use, and implementation of rainwater harvesting and irrigation saving agriculture.

Improve the ecological environment in arid areas. Carry out the work of returning farmland to forests, grasslands and lakes according to local conditions to curb the deterioration of the ecological environment and reduce the harm of drought.