Basic situation of drought in northern China
Since the winter of 2008, severe drought has occurred in the main wheat producing areas in northern China, which has greatly affected agricultural production. 15 provinces and cities have drought, and the winter wheat areas in 8 provinces are concentrated. As of February 7, 2009, the drought-affected area of crops in China was 65.438+0.63 billion mu, which was 65.438+0.654 3.8+0.00 billion mu more than normal. There are 4.42 million people and 2.22 million large livestock who have difficulty drinking water due to drought. The drought-affected areas in winter wheat areas of Hebei, Shanxi, Anhui, Jiangsu, Henan, Shandong, Shaanxi and Gansu provinces totaled 65.438+0.52 billion mu, accounting for 95% of the drought-affected areas of crops in China, including 48.79 million mu of severe drought. Among the seven major wheat-producing provinces affected by the disaster, Henan has the largest wheat planting area, accounting for a quarter of the country's output. However, its disaster is also the most serious. The drought-affected area of wheat in the province is more than 410.5 million mu, and it is seriously affected by drought of 7 million mu. More than 10,000 people in hilly areas10.3 have temporary drinking water difficulties. In recent days 1 10, the effective precipitation in Henan Province did not exceed 15 mm, and 500,000 mu of wheat seedlings died. The drought-affected area in Anhui province reached 259 1 10,000 mu, of which 65.438+0.074 mu was severely drought, and the direct economic loss was nearly 65.438+0.6 billion yuan. In Shandong, since 2009, the precipitation in the whole province is only 1mm, which is nearly 90% less than the same period of last year. Sixty percent of the province's wheat fields are affected by drought, covering an area of 33.28 million mu. The drought-stricken area in Gansu Province is 46,000 square kilometers. 400,000 people in Hebei have difficulty drinking water, and Shijiazhuang has experienced a rare drought in the past 50 years. In addition, Shanxi, Qinghai, Hubei and other provinces and cities *** 15 all suffered from extensive drought to varying degrees.
Characteristics and causes of drought in northern China
Since the end of June 2008 (5438+065438+ 10), the precipitation in winter wheat areas in China has been obviously less, and the drought has continued to develop. In addition, several severe cooling weather processes since winter have caused drought and freezing, which seriously affected the normal development of winter wheat and showed several characteristics:
(A) the characteristics of drought in the northern region
1. The drought-affected area is large. The impact of this drought is very wide. The total area of crops affected by drought in the whole country and the three northern arid areas reached 6543.8 0.63 billion mu, which was 6543.8 0.65 billion mu more than normal. The duration, scope and severity of this drought are also rare in history.
2. The drought-stricken areas are concentrated and the main producing areas are affected. At present, there are different degrees of drought in 15 provinces and cities in China, but the drought-affected areas in winter wheat areas in Hebei, Shanxi, Anhui, Jiangsu, Henan, Shandong, Shaanxi and Gansu account for 95% of the country, which is very concentrated. From the location, the drought mainly affected the winter wheat planted in the northern part of Huanghuai and the middle and lower reaches of the Yangtze River. Drought-stricken areas are mainly concentrated in North China, Huanghuai and the northern winter wheat area in the eastern part of northwest China. The drought-affected areas in Hebei, Shanxi, Anhui, Jiangsu, Henan, Shandong, Shaanxi, Gansu and other provinces account for 95% of the country's drought-affected areas, among which the drought-affected areas of winter wheat account for 93% of the drought-affected areas of field crops. The drought-affected area of winter wheat in six provinces reached 40%-70% of the field crops, and the severely drought-affected area of dead leaves or frozen tillers reached 53.72 million mu, exceeding 30%.
3. Continuous drought in autumn and winter. Since the emergence of winter wheat, there has been no effective precipitation in North China, Huanghuai, Northwest China, Jianghuai and other places for more than three months, which is 70-90% less than the same period of normal years, and the precipitation in some areas is close to or exceeds the historical extreme value. Generally speaking, precipitation occurs once every 30 years in winter wheat areas and once every 50 years in extremely dry areas. The northern wheat region suffered from a rare drought in autumn and winter for many years. At present, North China, Huanghuai, Jianghuai and other places have generally reached moderate to severe drought, and some areas have reached a particularly heavy level.
The drought is very serious. According to the investigation of agricultural departments in major grain-producing provinces, due to the lack of effective rainfall for a long time, frequent windy weather and serious soil moisture loss, 3- 10 cm dry soil layer appeared in a large area in the northern wheat area, and the drought is still developing.
5. Drought and freezing overlap. While the drought continues to develop, since the beginning of 65438+ in February, 2008, cold air activities have been frequent, and there have been many large-scale cooling processes, especially in 20091October 20 -25, most parts of China were hit by cold waves, and the cooling range reached 8℃- 12℃, and some areas reached1.
(b) Analysis of the causes of drought
1. The influence of natural factors
(1) Meteorological factors: Most parts of China belong to the Asian monsoon region, and the precipitation is affected by land and sea distribution, topography, monsoon and typhoon, and the regional distribution varies greatly. The seasonal distribution in the year is unbalanced, and the interannual changes are also great, which is one of the reasons why floods and droughts are prone to occur. Since the winter of 2008, there has been little rainfall and high temperature. There is no rain or snow for more than 80 days in most parts of North China, Northwest China, Huanghuai and Jianghuai, and some areas exceed 100 days. According to the meteorological department's assessment, the light rain once every 30 to 50 years. Last winter, from the first ten days of 165438+ to the middle of 12, the temperature in North China, Huanghuai and the eastern part of northwest China was 2-4℃ higher than normal, and the soil moisture evaporated greatly and lost quickly. Since February 65438 last year, there have been three large-scale cooling processes, especially before the Spring Festival. The cooling range is 8- 12℃ in most areas and 17-20℃ in some areas. As the temperature rises rapidly after the Spring Festival and the rainfall continues to be less, spring irrigation has been started in winter wheat areas in various places in advance, and some have increased irrigation times and increased and concentrated water consumption. In addition, the inflow and storage capacity of rivers in some areas are less, which leads to the shortage of drought-resistant water sources.
(2) The imbalance of water resources combination is also the cause of drought and water shortage, especially in the north, where there is more land and less water resources. Based on the average amount of water resources per mu of cultivated land, the national average is more than 1.800 m3/mu, but the Yellow River and Huaihe River basins are only more than 300 m3/mu, and the Liaohe River and Hailuan River basins are even less, about 200 m3/mu respectively, which cannot meet the demand for farmland water. Due to the above-mentioned natural factors such as climate and geography, the drought characteristics in different regions of China are determined: the spring drought in Qinling Mountains and the north of Huaihe River is prominent, commonly known as the "once-in-nine-year spring drought". This is the critical period of winter wheat growth and early autumn crop sowing, and irrigation or other drought-resistant measures are often needed to ensure the water demand of crops.
2. The role of human factors
(1) The deterioration of ecological environment and unreasonable utilization of water resources have weakened the drought resistance of water conservancy projects. Due to the increase of population, the per capita cultivated land area is decreasing. In the case of low grain output and farmers' living difficulties, unreasonable land reclamation activities on steep slopes are more serious and grass slopes are reduced. In addition, factors such as road construction, urban and rural construction, and disorderly stacking of waste residues and wastes have accelerated soil erosion, lost topsoil, thinned the soil layer, and reduced the potential drought resistance of soil. At the same time, the lost sediment continuously silts reservoirs and weirs, reducing the water storage capacity of reservoirs and ponds and reducing the water supply capacity of water conservancy projects.
(2) The contradiction between supply and demand of water resources has intensified. With the development of production, the increase of human living demand, the improvement of multiple cropping index of cultivated land, the adjustment of crop varieties and the increase of output, the agricultural water consumption has increased greatly, the contradiction between supply and demand of water resources has become more tense and the drought problem has become more serious. For example, many places used to grow crops in one season, but now they grow crops in two seasons a year. In particular, the crop yield has been greatly increased, and the water demand has also increased accordingly. 1949 The average grain yield per mu of cultivated land in China was only 86 kg, and in 2008, the grain yield per mu reached 330 kg. If calculated according to the amount of water needed to produce 1 kg grain, the water demand of crops per mu of cultivated land is several times higher than that in the early days of liberation. This is also one of the reasons why the average annual drought-affected area has been increasing since the founding of New China for decades.
(3) Insufficient capital investment, and the construction of farmland water conservancy facilities lags behind. Drought needs to be solved by increasing irrigation and water conservancy facilities, and insufficient capital investment leads to imperfect infrastructure construction such as irrigation and water conservancy in many places. Either there is no canal, or the waterway is abandoned; Either there is no well, or the well collapses; Otherwise, there is no electricity in the well, and drought resistance can only be carried by shoulders. In April 2008, Director Zhao Mingji of the Agriculture Department of the Ministry of Finance disclosed that the existing irrigated area in China was 928 million mu, of which 868 million mu was effective, accounting for only 46% of the total cultivated land in China. In recent years, the national water conservancy investment is often more concentrated in the construction of large-scale water conservancy projects such as river regulation, but the last mile problem, which really has the greatest impact on farmers, has not been effectively solved. In addition, after the reform of rural taxes and fees, the "two jobs" were cancelled, and the number of working days used for small-scale farmland water conservancy construction decreased by about 4.5 billion every year, equivalent to 90 billion yuan per year. Farmland water conservancy construction activities, which originally relied mainly on farmers to raise funds and invest labor, have been greatly affected. There are still many places that have been relying on farmland water conservancy facilities built in the 1960s and 1970s. The construction of irrigation and water conservancy facilities is lagging behind, which seriously affects the drought resistance effect in northern China.