How will the rainfall in southwest China (preferably Guangxi) change in the next decade compared with the present?
The reason why Guangxi is getting warmer and warmer is simply the weak cold air activity in winter. Further discussion is that global warming leads to some extreme weather events. Due to the rising temperature, the intensity of typhoons affecting China has increased. Last year, Guangxi was slightly affected by low temperature, which is the positive side of high temperature, but on the other hand, too warm will also bring negative effects. For example, the severe autumn drought in Chongzuo and Nanning last year was related to high temperature and little rain for several days. The influence of temperature change on agriculture is far-reaching. For example, winter is not cold enough, the output of litchi and longan is not as good as before, and other agricultural products are harvested.
Guangxi is a province rich in water resources in China. Water resources mainly come from river runoff and inflow into rivers. River runoff includes surface water and groundwater discharge, and there is a mutual transformation relationship between river runoff and groundwater recharge. The average total water resources in Guangxi for many years is 65.438+0.88 billion cubic meters, accounting for 7.654.38+0.2% of the total water resources in China, ranking fifth in the country. The incoming water is 710.67 billion cubic meters. 1996, the per capita water resources in Guangxi were 4 138 cubic meters, 7.2 cubic meters per hectare, and the degree of water resources development and utilization was 23% of river runoff and 9.2% of groundwater.
(B) the distribution of water resources
There are 937 rivers with a basin area of more than 50 square kilometers in Guangxi, with a total area of 2,364,275 square kilometers, including 69 rivers with a basin area of 1 10,000 square kilometers. The main rivers belong to Xijiang River system in the Pearl River basin, Dongting Lake system in the Yangtze River basin, the direct current flowing into the sea in southern Guangxi and the red river system in Baidu River.
1. Xijiang River system
The main rivers in Xijiang River Basin are Nanpanjiang, Hongshui River, Qian Xun, Yujiang, Liujiang, Gui Jiang and Hejiang. The total area of Xijiang River basin is 304,900 square kilometers, of which the catchment area in Guangxi is 202,400 square kilometers, accounting for 85.7% of the total water area, and the total water resources account for about 85.5% of the total water resources in Guangxi.
Nanpanjiang River is the main source of Hongshui River in the Pearl River Basin and the mainstream of Xijiang River. The river is 936 kilometers long, and the basin area in Guangxi is 4 162 square kilometers. The average total water resources for many years is 65.438+94.3 million cubic meters, and the water production modulus is 467,000 cubic meters/square kilometer.
Hongshui River. From sugarcane fragrance to leye county, Tiane, Nandan and Laibin counties in Guangxi, to Shilong Town and Liujiang Town in Xiangzhou County? The river is 659 kilometers long and the catchment area of the basin is 43,790 square kilometers. The average total water resources for many years is 32.499 billion cubic meters, and the water yield module of the basin is 746,700 cubic meters/square kilometer.
Jiang Xun, Guizhou. Qianhai and Jiangzi River start from Sanjiangkou, Shilong Town, Xiangzhou County, flow through Wuxuan and Guiping to Wuzhou, and join Guijiang Day. The river length is 172km, and the catchment area is 2 1 680km2. The water yield modulus is 679,000 cubic meters per square kilometer, and the average total water resources for many years is 65.438+0.473 billion cubic meters.
Yujiang county. Yujiang River originated in Yangmeishan, Guangnan County, Yunnan Province, and is the largest tributary of Xijiang River Basin. The catchment area of the basin is 90,800 square kilometers (including the area in Viet Nam), including 79,207 square kilometers in China and 68 125 square kilometers in Guangxi. The total water resources in Yujiang River Basin is 37 1 100 million cubic meters, and the water production modulus is 544,600 cubic meters/square kilometer.
Liujiang. Liujiang River originates from Lina 99 Beach in the south of dushan county, Guizhou Province, and its upstream is called Duliujiang River, which is the second largest tributary of Xijiang River system in the Pearl River Basin. The river spans Guizhou, Hunan and Guangxi provinces, with a drainage area of 58,270 square kilometers, total water resources of 37.392 billion cubic meters, inflow of 8.74 billion cubic meters and water production module of 892,300 cubic meters/square kilometer. It is a river rich in water resources in Guangxi. Gui Jiang Gui Jiang and Hejiang are located in the east of Guangxi, with a drainage area of 26,927 square kilometers and total water resources of 27.47 billion cubic meters. Among them, Gui Jiang is 65.438+0.827 billion cubic meters and Hejiang is 9.2 billion cubic meters. The water yield modulus is 6.5438+0.02 million cubic meters/square kilometer, which is one of the areas with rich water resources in Guangxi, and the precipitation comes earlier than other areas.
2. Yangtze River system
Xiangjiang River and Fuyi Water are located in the northeast of Guangxi, which flows into Dongting Lake in Hunan and then into the Yangtze River. The catchment area in Guangxi is 8.283 square kilometers, accounting for 3.5% of Guangxi's area, and the total water resources are 9.306 billion cubic meters.
3. Coastal rivers in southern Guangxi
The main coastal rivers in southern Guangxi are Nanliu River, Dafeng River, Wangqin River, Fangcheng River, Maoling River and Beilun River. The biggest river is Nanliu River. Beilun River is an international river, followed by Qinjiang River and Fangcheng River. The rainwater collection area of coastal rivers flowing directly into Beibu Gulf is 23,230 square kilometers, accounting for 10.2% of the total land area of Guangxi. The average water resources for many years is 27.36 billion cubic meters (including the source of Baidu River and western Guangdong). The existing water conservancy conditions in this area are good and the utilization rate of water resources is high. However, the temporal and spatial distribution of rainfall is very uneven, generally concentrated from May to September, accounting for about 80% of the annual rainfall. In winter and spring, some small rivers dry up, resulting in insufficient industrial and domestic water supply in coastal areas, which has an impact on economic development and construction.
Guangxi is located in a low latitude area, bordering tropical oceans in the south, Nanling Mountains in the north and Yunnan-Guizhou Plateau in the west. There are many rivers in the territory and the geographical environment is complex. Under the comprehensive action of solar radiation, atmospheric circulation and underlying surface, climate types have the following characteristics:
(1) Climate types are diverse, with long summer and short winter. As far as climate zoning is concerned, the northern part of Guangxi belongs to the tropical climate of Central Asia and the southern part belongs to the tropical climate of South Asia. Topographically, northern and western Guangxi have the general characteristics of mountain climate, with obvious "three-dimensional climate" and diversified microclimate ecological environment. However, southern Guangxi has a warm and humid maritime climate. In Guangxi, winter is short and summer is long, and the annual average temperature is between 16℃ and 23℃. Measured by the average temperature, the summer in the north is as long as 4 months to 5 months, and the winter is only about 2 months. May to the south 10 is summer and winter is less than two months. There is almost no winter in coastal areas.
(2) Rain and heat resources are abundant and in the same season. The annual rainfall in Guangxi is between 1 0,000 mm and 2,800 mm, especially in Dongxing District of Fangchenggang City, reaching 2,822.7 mm, and the least rainfall is in Tianyang County, which is around 1, 100 mm. The total annual solar radiation is 90 kcal ~/kloc-0,000 kcal/. The daily average temperature is ≥ 10℃, the accumulated temperature is between 5000℃ and 8300℃, and the duration is 240 days to 358 days. The distribution of precipitation and heat resources generally increases from north to south. The rainfall from April to September accounts for 75% of the annual rainfall, and the rainy season coincides with the hot season. Rain and heat in the same season are more conducive to agricultural production.
(3) The climate is changeable and disastrous weather is frequent. The abnormal advance and retreat of monsoon in Guangxi often leads to great changes in rainfall and temperature, and severe weather such as drought and flood, "two chills" (cold in late spring and cold dew wind), typhoon and hail frequently occur. There is a spring drought in western Guangxi with a frequency of 60% ~ 90%, and an autumn drought in eastern Guangxi with a frequency of 50% ~ 70%. The rainy season is heavy and the rainstorm is too concentrated, and floods occur every year, especially in the coastal areas of southern Guangxi and Rongjiang River basin. However, in the spring and autumn rainy season, influenced by the strong cold air from the north to the south, there are cold dew in spring and autumn almost every year, which harms agricultural production. Windy weather occurs from April to July every year, with a large scope and degree of influence. In addition, the perennial hail in western Guangxi is not conducive to the winter production of crops and fruit trees.
Types and distribution of climate resources
1. heat resources
The average annual temperature in Guangxi is between 17℃ and 22℃, and the average daily temperature in Leng Yue is between 5.5℃ and 1 5.2℃. The hottest month in July is between 27℃ and 29℃. Over the years, the extreme maximum temperature in various places is mostly from 36℃ to 42℃, and the extreme minimum temperature is generally from MINUS 6℃ to 0℃. The annual average temperature of 65438+ 10 and July is gradually increasing from north to south, and gradually decreasing from valley plain to hilly and mountainous areas. Ziyuan County with the lowest annual average temperature is 6.2℃ higher than Beihai City with the highest annual average temperature. The 2 1℃ isotherm is roughly consistent with the 24-degree latitude in western Guangxi and the tropic of cancer in southeastern Guangxi. The south of the line basically belongs to the tropical climate zone of South Asia, in which the annual average temperature in the southern coast and the left and right valleys is greater than 22℃; North of the 2 1℃ isotherm, it belongs to the tropical climate zone of Central Asia. Judging from the start and end dates, duration days and accumulated temperature of each boundary temperature, there are great differences in Guangxi. The accumulated temperature is ≥ 10℃, and the southern coast and the left and right river valleys are as high as 8000℃, and the highest is 8306℃; Resources, leye county, Nandan and so on. The mountainous area in northern Guangxi is relatively low, which is lower than 6200℃ and the lowest is 4975℃, with a difference of 3300℃. Its distribution characteristics are similar to the annual average temperature, which is higher in southern Guangxi than in northern Guangxi, higher in western Guangxi than in eastern Guangxi, and higher in valley plains than in hilly and mountainous areas. The first-day distribution law of accumulated temperature ≥ 10℃ is the same as that of accumulated temperature ≥ 10℃, but the whole day is opposite, but there is little difference between east and west. The first day in the coastal areas of southern Guangxi began before mid-February, about 40 days earlier than in the mountainous areas of northeastern Guangxi, and the left and right valleys of western Guangxi were earlier than the end of 1 year, and 20 days earlier than in Wuzhou and Yulin areas of eastern Guangxi. The distribution of daily average temperature ≥ 10℃ has corresponding characteristics, that is, it is long in the south and short in the north, long in the west and short in the east, long in the valley plain and short in the hilly and mountainous areas. Hepu in southern Guangxi is 340 days long, 77 days longer than Guilin in northern Guangxi, 44 days longer than Wuzhou in eastern Guangxi, and 25 days longer than Jinxiu Mountain in Liuzhou Basin at the same latitude. The frost-free period varies greatly from 284 days to 365 days, and its distribution law is consistent with the annual average temperature. Among them, the frost-free period in most parts of Qinzhou, Yulin and Nanning, southwest of Hechi and southeast of Baise is more than 340 days, especially in southern Qinzhou, Yulin, southeast of Du 'an and the left and right river valleys, which is about 360 days, and there is basically no winter. The frost-free period in Jinxiu, Ziyuan, Guanyang, Xing 'an, Hexian and leye county is short, but it also reaches 284 to 298 days. The rest of the area is mostly 300 to 340 days.
Low temperature seedling rot in spring and cold dew wind in autumn are the main agro-meteorological disasters in Guangxi. From February to April in spring, there is strong cold air in the north going south and meeting with warm and humid air in the south, resulting in long-term low temperature and rainy weather, affecting the timely sowing of early rice and even causing a large number of rotten seedlings. According to statistics, 10 has 8 rotten seedlings. Around the Cold Dew Festival, cold air from the north began to invade the south. When there is strong cold air, it will also cause cold weather (called cold dew wind), which will affect the normal heading, flowering and filling of late rice and increase the empty shell rate. For conventional rice varieties, the start date of cold dew wind is from mid-September to early June 10 in northern Guangxi, 10 in central Guangxi and 10 in southern Guangxi.
2. Precipitation resources
Guangxi is one of the areas with more precipitation in China. The average annual precipitation in most areas is 1.200mm ~ 2000mm, and the temporal and spatial distribution is quite different. The three rainfall centers are located near Dongxing, Zhaoping and Yongfu respectively. The average annual precipitation near each center is above 1.900mm, of which Dongxing is as high as 2822.7mm, and the average annual precipitation is below 1.200mm in Youjiang basin with Baise as the center, Longlin and Xilin in the upstream, Mingjiang and Zuojiang basins with Ningming as the center. The rest area is between 1, 200mm and 1, 900 mm. In addition to uneven regional distribution, the precipitation in the same place varies greatly in different years. For example, in Zhaoping 1973, the precipitation reached 2923.3 mm, while in 1984, it was only 1.304.8 mm, the former was more than twice as much as the latter.
The number of precipitation days (daily precipitation is greater than or equal to 0. 1mm) also varies from place to place, with an average of more than 180 days in northern Guangxi and less than 140 days in Youjiang Valley and southern coastal areas. Among the days of precipitation, the days of rainstorm account for 10% to 18%, and the days of heavy rainstorm account for 2% to 8%. The seasonal distribution of precipitation is also uneven. May to September is the rainy season, and the precipitation accounts for 75% of the whole year. The dry season is from June 5438 to April of the following year, and the precipitation only accounts for 25% of the whole year. Because the annual and seasonal precipitation changes greatly, droughts and floods often occur, and droughts occur twice every three years on average. There are more than 8 spring droughts in Baise, western Nanning, Qinzhou and Nanning, among which the spring droughts in Baise and Tian Yang 10. There are many droughts in autumn in the northeast of Guangxi, which occurred in May-July of 10. During the rainy season, especially from June to August, there are floods every year. The southern coast of Guangxi, Rongan, Rongshui, Yongfu, Bama, Duan and other places, can be called the three major flood centers in Guangxi, with an average of 2 to 6 times a year.
3. Light energy resources
Guangxi has strong solar radiation and relatively little sunshine. The annual average total solar radiation is between 90 kcal/cm2 and 130 kcal/cm2. The Youjiang Valley and its western region, the southeastern regions of Wuzhou and Yulin, Ningming, Shangsi and Nanning on the north side of Shiwan Mountain have the largest annual radiation, exceeding 1 10 kcal/cm2. The mountainous area in northern Guangxi is the least, with the total annual discharge below 100 kcal /cm2, and the resources, Rong 'an and Nandan are less than 90 kcal /cm2.
Rich radiation resources are only beneficial, and less sunshine is not good for crop growth and development. The average annual sunshine hours in Guangxi are mostly between 1.300 hours and 2250 hours. There are many in the left and right river valleys, southeast and south coastal areas of Guangxi, ranging from 1.800 hours to 1.940 hours, and Weizhou Island has the most, with 2253 hours. The resources in northern Guangxi, such as Longsheng, Sanjiang, Nandan, Tian 'e and Jinxiu in central Guangxi, are rainy in winter and spring, and the annual sunshine hours are only 1.300 hours, which is the least in the whole region.
4. Wind energy resources
According to the relevant analysis results, along the Gui Xiang-Li Zhan railway, east of Damiao Mountain, Daming Mountain and Shiwan Mountain, and west of Dayao Mountain to Darong Mountain, the terrain is relatively flat and open, which is the main channel for winter wind to go south and summer monsoon to go north, and is a high-value area of wind energy resources in Guangxi. Among them, Qinzhou coastal area and Gui Xiang corridor area are rich in wind energy resources, which has the value of using wind energy to generate electricity, process agricultural and sideline products and lift water. The area west of Damiao Mountain, Daming Mountain and Shiwan Mountain is located in the southeast of Yunnan-Guizhou Plateau, with relatively closed terrain and poor wind resources, which is generally of no development and utilization value. Only in Tian Yang, Tiandong, Du 'an, Napo and other places in Youjiang Valley, wind energy resources have certain development value due to the narrow tube effect of topography. In addition, in some mountainous areas, such as mountain passes or mountain tops, the wind speed is relatively high, which also has certain utilization value.
To sum up, the climatic conditions in Guangxi have advantages and disadvantages. Therefore, in the process of developing large-scale agricultural production, starting from the local climatic conditions, adapting to the local climate, seeking advantages and avoiding disadvantages, and rationally developing and utilizing climatic resources are important links that must be paid attention to in implementing economic construction, especially in developing "three high" agriculture. Guangxi is rich in climate resources and diverse in ecological environment. On the premise of rationally adjusting the industrial structure and not relaxing the grain production, we should actively develop diversified economy, focus on developing local famous, excellent and special products, develop foreign exchange-earning agriculture, establish cash crop bases and create higher agricultural economic benefits.