What characteristics of my country's water resources does the drought in the north reflect? Urgent urgent....
my country’s Drought Characteristics and Defense
Most of our country is located in the East Asian monsoon region, with complex weather and climate. It is one of the most climate-vulnerable areas in the world and is also the most severely affected by meteorological disasters. one of the countries. Meteorological disasters in my country are characterized by many types, wide distribution, high frequency, long duration, serious secondary disasters, large economic losses, and many casualties.
Drought is the most common climate disaster in my country that has the greatest impact on agricultural production. The drought-stricken area accounts for more than half of the total crop-affected area, and the proportion of severe drought years is as high as 75%. According to incomplete statistics, from 206 BC to 1949, there were 1,056 major droughts in my country, with an average of one major drought every two years. For example, the severe drought in Shaanxi from 1928 to 1929 caused 940 droughts in the entire territory. The disaster killed 2.5 million people out of 10,000 people. After the founding of the People's Republic of China, the country invested heavily in building water conservancy facilities, expanding irrigation area, greatly improving agricultural production conditions, and improving the ability to prevent drought disasters. However, due to climate conditions and social and economic development, population growth, agricultural, industrial and urban domestic water use has increased sharply, coupled with the deterioration of the water environment, the amount of available water has decreased. The frequency of droughts in my country is still very high, with large affected areas and drought disasters. aggravating trend. According to statistics, in the past 50 years, the average annual drought-affected area in my country has reached 22.17 million hectares. In the 1990s, with the intensification of global climate warming, droughts occurred frequently in northern my country, with the average annual drought-affected area rising to 27.11 million hectares, with severe droughts reaching 40.54 million hectares in 2000 and 38.47 million hectares in 2001.
1. Distribution characteristics of drought in my country
1. Temporal and spatial distribution characteristics
Drought may occur throughout the year in my country. Spring drought mainly occurs in the Huanghuai River Basin and the areas north of it. The probability of spring drought in North China is about 70%. There is a saying that "spring drought occurs nine times out of ten years". In some years, the spring drought lasted until June and July, resulting in consecutive spring and summer droughts, which had a serious impact on agricultural production, such as in 1962, 1972, and 1997. In 1965, there were even consecutive droughts in spring, summer, and autumn, which had an even more severe impact on agricultural production.
Summer drought is usually divided into early summer drought and late summer drought. Droughts in early summer mostly occur in the north. Fudrought is a drought during the "three days" in midsummer. It mostly occurs in the Qinling Mountains and south of the Huaihe River to the northern part of South China, and is more common in the middle and lower reaches of the Yangtze River. Generally, the impact of latent drought is not very serious. The damage will be serious only when the drought lasts until September, October or November, that is, when continuous droughts occur in summer and autumn.
Autumn drought mostly occurs in central and southern China, and has a greater impact on the growth of late rice in the south. The autumn drought in the north has little impact on crops, but it will be detrimental to winter wheat sowing and emergence.
Winter drought mainly occurs in southern China and the southwest and eastern regions. Because crops still grow here in winter and require more water, winter drought will occur in years with little rain. In some years, the drought lasts for a long time, and the winter drought can last until the early spring of the next year. For example, from November 1998 to April 1999, and from October 2004 to April 2005, consecutive droughts occurred in some areas of South China that lasted for autumn, winter and spring. , which has a great impact on industry, agriculture and domestic water supply. In southwest China, continuous droughts in winter and spring can last for 4 to 5 months, and sometimes continuous droughts occur in autumn, winter, and spring. For example, it lasted for 7 months from November 1959 to May 1960.
Affected by inter-annual and cyclical fluctuations in precipitation, the occurrence of drought also changes in stages. Since 1951, the area affected by drought in my country has shown an upward trend, with large changes year by year. In the 1950s and 1960s, the area affected by drought was small. In the 1970s, the area affected by drought nearly doubled compared with the previous two decades. In the 1980s, the area affected by drought decreased slightly, but it has increased significantly since the 1990s. In the past 50 years, there have been 13 years in which the area affected by drought exceeded 30 million hectares, including 6 years since the 1990s. Generally speaking, there are three low-value periods and four high-value periods for the drought-affected area in my country. From 1951 to 1957, 1963 to 1970, and 1982 to 1984, the area affected by drought each year was generally less than 20 million hectares; in 1959-1961, 1971-1981, 1986-1989, and 1999-2001, the area affected by drought each year was generally less than 20 million hectares. More than 25 million hectares.
2. Five drought centers in my country
Drought can occur in various parts of my country, but the frequency and degree of occurrence are different. Statistics from the past 50 years show that there are five obvious drought centers in my country:
(1) Northeast arid area. Drought in this area mainly occurs in spring and summer from April to August. The probability of spring drought is 66% and the probability of summer drought is 50%.
(2) Huang-Huai-Hai arid area (eastern northwest and North China). This area has less precipitation and high variability. It is the largest drought area in my country, and the number of droughts also ranks first in the country. Droughts may occur from March to October during the crop growth period. In a few years, spring, summer, and autumn droughts may occur in some areas, but spring droughts are the main ones and occur to varying degrees almost every year.
(3) Yangtze River Basin area. Drought can occur in this area from March to November, but it is mainly concentrated in summer and autumn. Drought is more likely to occur from July to September, and latent drought is the most harmful.
(4) South China.
Drought can occur in this area throughout the year, but because the rainy season comes early in South China and typhoons often rain in summer and autumn, drought mainly occurs in late autumn, winter and early spring. In most years, the drought lasts for 3 to 4 months, and the longest is 7 to 8 months.
(5) Southwest region. The scope of drought in this area is small. The drought generally starts in October or November of the previous year and ends in April or May of the next year. It lasts until June in some areas in some years, but the drought mainly occurs in winter and spring. .
2. The impact of drought
Drought is a climate disaster. It is one of the important factors restricting the sustainable development of the economy and social security, and affects human society. all aspects of economic activity. Drought causes soil water shortage, which affects the normal growth and development of crops and reduces yields. Secondly, it causes insufficient water resources, making it difficult for people and animals to drink water, causing urban water supply shortages and restricting urban development. Long-term drought can also lead to the deterioration of the ecological environment. Drought can be divided into soil drought and atmospheric drought. If both occur at the same time, the damage will be more serious.
Drought disaster is one of the most important natural disasters in our country. Every severe drought that has occurred in history has brought serious disasters to the Chinese nation. In the past century, there have been severe drought years in my country such as 1900, 1928-1929, 1934, 1956-1961, 1972, 1978 and 1999-2001. There were three consecutive years of drought from 1959 to 1961, with disasters affecting 10 to 15 provinces (autonomous regions and municipalities). The average drought-stricken area was 36.59 million hectares, 15.33 million hectares were affected by disasters, and grain production was reduced by 61.15 billion kilograms.
Drought has caused increasing losses to the country’s economic construction and people’s lives and property, seriously affecting social security, national economic development and the people’s living environment. With economic development and population growth, the absolute value of losses caused by drought shows a significantly increasing trend. In 2000, a nationwide drought occurred in my country, especially the severe spring and summer drought in the area north of the Yangtze River from February to July. The drought was widespread, long-lasting, and severe. The drought period lasted for half a year in North China and the eastern part of northwest China. In 2000, the country's drought-stricken area reached 40.54 million hectares, the highest since the founding of the People's Republic of China. Among them, 8 million hectares suffered no harvest. Nearly 60 billion kilograms of grain were lost due to drought, and cash crops were lost 51 billion yuan. Its impact exceeded the natural disasters in the three years from 1959 to 1961. disaster.
Drought and water shortage seriously restrict the development of rural economy. Drought and water shortages cause drinking water difficulties for millions of people every year. The severe drought that occurred in the northern region from February to May 2001 not only caused more than 22 million hectares of farmland to be affected by drought, but also caused 15.8 million people and 11.4 million large livestock to have temporary drinking water shortages. difficulty.
Drought, especially consecutive droughts, not only brings the most obvious and direct harm to agricultural production and causes agricultural and food harvests, but also has far-reaching adverse effects on water resources, ecological environment, economic and social development, etc. Influence. The Yellow River has been drying up frequently since the 1970s. The most serious one was in 1997, when Lijin Hydrological Station in the lower reaches of the Yellow River was hit by a severe drought and was dry for 226 days throughout the year. The longest dry river section was more than 700 kilometers. The interruption of the Yellow River has had a serious impact on people's lives, industrial and agricultural production, and the ecological environment in the basin. Lack of water resources, serious shortage of water for industrial production and domestic use, has led to the deterioration of the ecological environment, land desertification and salinization, further leading to intensified sandstorms, continued reduction of forest coverage, and increasingly serious grassland degradation. Due to lack of water resources, excessive exploitation of groundwater has also led to land subsidence.
3. Cases of severe drought in the past 10 years
In 1992, there was a severe summer drought in the Huanghuaihai Sea. From mid-May to early July 1992, most of the Huang-Huai-Hai region continued to experience drizzle, with total precipitation generally only 20 to 50 mm, 50 to 80% less than the same period in normal years. Parts of the lower reaches of the Yellow River and Huaihe River were once cut off. Severe summer droughts occurred in Shandong, Henan, Hebei, Shanxi, northern Jiangsu, and northern Anhui, with the drought-affected area reaching more than 13 million hectares.
In 1994, there was a serious drought in the Jianghuai and Sichuan basins. In 1994, the precipitation in the Jianghuai region from late June to mid-August was only 100 to 200 mm. The precipitation in most of the Sichuan Basin and southern Shaanxi, Guanzhong, Longdong, Longnan and other places was only 50 to 100 mm from mid-July to mid-August. The weather was 50% to 80% less than the same period in normal years, and droughts occurred to varying degrees. Among them, Anhui and Jiangsu provinces have suffered the most serious droughts since the founding of the People's Republic of China. Shaanxi, Sichuan, Henan and other provinces have also suffered from severe droughts.
In 1997, there was a serious summer drought in the northern region. In the summer of 1997, most of the north suffered from continuous low rainfall and high temperature. The precipitation was generally 150-300 mm, which was 20-40% less. Among them, some areas in North China and Northwest China were 50-70% less, and the drought-stricken area reached more than 20 million people. hectares, of which more than 9 million hectares were severely drought-stricken. A severe summer drought that was rare since the founding of the People's Republic of China occurred.
In 2000, there was a widespread spring and summer drought in the north. From February to July 2000, precipitation in most areas north of the Yangtze River was significantly less than the same period in normal years. In addition, the temperature was higher than the same period in the year, and windy and sandy weather was frequent, leading to a large-scale spring drought. After the beginning of summer, most of North China, the eastern part of northwest China and other places still have little rain. Coupled with the persistent high temperature, there will be continuous droughts in spring and summer. In 2000, drought affected a wide range of areas across the country, lasted for a long time, and was severe. Jilin, Heilongjiang, Liaoning, Inner Mongolia, Shanxi, Hebei, Tianjin, Shandong, Gansu, Shaanxi, Anhui, Hubei, Ningxia and other provinces and cities are suffering from a wide range of droughts and serious drought conditions.
This year, the drought-affected area across the country reached 40.54 million hectares, the largest since the founding of the People's Republic of China.
In 2001, there was a drought in the spring and summer in the north. From February to early June 2001, most areas north of the Yangtze River experienced abnormally low precipitation, generally high temperatures, high evaporation, and rapid loss of moisture in farmland. A large-scale sustained drought occurred, including Shanxi, Shandong, Henan, and Liaoning. The drought is particularly severe in provinces such as Hebei and Hebei. This is another large-scale severe drought in the northern region following the severe droughts in 1997, 1999 and 2000. Due to successive years of drought and lack of rain, water conservancy projects have insufficient water storage and groundwater has not been significantly replenished, resulting in increasingly serious water shortages.
In 2004, there was a severe autumn drought in South China and the middle and lower reaches of the Yangtze River. Since the beginning of autumn in 2004, precipitation has continued to be low in most parts of the south. From September to October, the average precipitation in the seven provinces (regions) of Guangdong, Guangxi, Hainan, Hunan, Jiangxi, Anhui, and Jiangsu was only 98 mm, which was the highest level in the same period in history since 1951. minimum value. In early November, the drought area expanded to almost the entire middle and lower reaches of the Yangtze River and southern China, with Guangxi, most of Guangdong, Hainan, southwestern Fujian, southern Hunan, eastern Hubei, most of Jiangxi, central and southern Jiangsu and Anhui, and northern Zhejiang reaching critical levels. Some areas have reached the severe drought standard, with crops affected by drought covering more than 5.1 million hectares, more than 9 million people having difficulty drinking water, and direct economic losses reaching more than 6 billion yuan.
4. Drought prevention and countermeasures
Optimize the agricultural structure according to the laws of drought. Agriculture is the most sensitive to drought and is most directly affected by drought. Properly arranging the structure of agriculture and animal husbandry can make use of limited resources to achieve both economic and ecological benefits. In areas with an annual rainfall of less than 400 to 500 mm, animal husbandry is the main industry and agriculture and forestry are supplemented. For example, in areas with an annual rainfall of more than 550 mm, crop varieties should be selected rationally and the crop planting structure should be adjusted to achieve benefits and avoid disadvantages.
Improve water resource utilization. Rational irrigation, scientific water use, and implementation of water-saving irrigation 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 damage of drought.