Traditional Culture Encyclopedia - Weather inquiry - Countermeasures for comprehensive control of karst drought

Countermeasures for comprehensive control of karst drought

(A) the current situation of drought in karst areas

Drought in Guangxi karst area is a typical natural disaster in karst area, and it is also an environmental geological problem that restricts the economic development in karst area.

According to historical records, from 1700 to 1949 * *, there were 152 droughts in Guangxi and 12 droughts in the whole autonomous region. After liberation, there were droughts in varying degrees in Guangxi almost every year. 1950 ~ 1990 During the four years1year, the average annual drought-affected farmland area was 56.84× 104hm2, and the average annual drought-affected farmland area was (5.48 ~155.2 )×/kloc-0. Among them, the affected area in 14 exceeds 66.67× 104hm2.

1963 is one of the most severe drought years. The annual average precipitation is 23.7% less than normal, and the evaporation is 25.3% more than normal. From June 1962 to June 1963, there was no rain. By the end of June, the effective storage capacity of the whole autonomous region was only 1.9× 108m3, accounting for only 10% of the total effective storage capacity. There are more than 2,200 small and medium-sized rivers cut off in the whole region, with 5 1 county with serious difficulties in drinking water for people and livestock, and water shortage 1.25 million people. The affected area is 155.2× 104hm2, the grain yield is reduced 10.9× 108kg, and the total economic loss is 21000000 yuan (current price).

From 1988 to 1990, severe drought occurred in Guangxi for three consecutive years. 1988 alternating drought and flood. More than 30,000 ponds and reservoirs dried up, and chengbihe reservoir released water below the water level to death. Eight large reservoirs and 63 medium-sized reservoirs such as Qingshitan, Naban, Kelan and Dawangtan have basically dried up. 140.85× 104hm2 farmland is affected by drought, with the affected area of 72.05× 104hm2 and the non-harvested area of 20.99× 104hm2. More than 4.3 million people and 610.7 million livestock have difficulty drinking water, and the grain production has been reduced by10.7.6×10.08 kg, resulting in a total economic loss of 930 million yuan (current price). 1989, the drought-affected area of crops in the whole region was 95.48× 104hm2, the disaster-affected area was 57.69× 104hm2, and the no-harvest area was15.81×104hm2. 1990 autumn drought caused 4,890 rivers to cut off, nearly 20,000 ponds and reservoirs dried up, and 100 people and 600,000 livestock had difficulty drinking water. The drought-affected area of crops is 123.7× 104hm2, and the affected area is 69.6 1× 65438.

In recent years, due to the abnormal climate, the frequency of drought phenomenon has increased, and the drought loss is still quite serious. According to statistics (Table 3-9), there have been two droughts in spring, summer and autumn in six years. Continuous drought in spring and summer 1 year; Spring drought for 2 years; 1 year has abundant rainfall, abundant water resources and mild drought.

Generally speaking, the drought in Guangxi is mainly spring drought and autumn drought, with less summer drought; Although there is little rain and dryness in winter, the temperature is low, the evaporation is small and the impact is small. Geographically, there are many droughts in spring in western and southern Guangxi, and many droughts in autumn in northern and central Guangxi. The main reason of climate drought is the abnormal atmospheric circulation when the monsoon advances and retreats, and the rainfall weather system has little or no influence on Guangxi. Generally, the year of severe drought was last autumn and winter with little rain, followed by spring and summer or summer and autumn with drought. For example, in 2004, affected by the continuous drought in 2003, there was a once-in-50-year drought, and the drought loss was very serious.

According to relevant data, there are 83 karst arid areas over 10,000 mu in Guangxi (attached figure 4, table 3- 10), with a total drought-affected area of 3,348,800 mu, accounting for 42 1% of the total cultivated land area (79,455,500 mu) in 2002, including 65,438+drought-affected paddy fields. It accounts for 38.95% and 6 1.05% of the total drought-affected area respectively. Among the drought-affected areas, 5 cities in karst plain area in central Guangxi account for 55.9%, and karst peak cluster area in southwest Guangxi accounts for 3 1.3%. Karst peak forests and hilly areas in northeast Guangxi account for10.1%; The karst area in eastern Guangxi is 2.7%. In addition, there are 24 arid areas, which are not only short of water and drought, but also threatened by floods. Most of these drought and flood areas are located in peak forest plains and peak forest valleys. The groundwater level rises in rainy season, and the surface and underground drainage are not smooth, which is easy to form waterlogging. The problem of karst immersion waterlogging in Guangxi is also regional, especially in northwest and central Guangxi. Under normal circumstances, waterlogging occurs once every two to three years, but in many places it is 1 time or several times a year. For example, towns such as Bai Shou and Yong 'an in Yongfu County, which are located in the rainstorm center of northern Guangxi, are waterlogged seven times a year on average. There are "nine floods in ten years" in Laping and Bana Karst Canyon in the Middle East of Guangxi, and 1 ~ 3 times a year in Yang Xiaoping Karst Plain. It is worth noting that in karst areas, due to the existence of dual or multiple spatial structures of surface and underground, surface runoff shows obvious seasonality, and underground runoff is often discharged into rivers in the form of turbulent flow, making it difficult to store water resources. A rainstorm immediately led to waterlogging, and it didn't rain for three days, and the drought was repeated. Therefore, this kind of karst area is often a sharp turn of drought and flood, which can be described as a sharp turn of drought and flood and a bad agricultural ecological environment.

Table 3-9 Drought and Drought Situation in Guangxi in Recent Six Years (1999 ~ 2004) Table 3-9 Drought Situation in Guangxi in Recent Six Years (1999 ~ 2004)

(According to Guangxi Water Conservancy Bulletin)

Table 3- 10 List of Dry Films over 10,000 mu in Karst Areas of Guangxi Table 3- 10 List of Dry Water Improvement over 10,000 mu in Karst Areas of Guangxi

sequential

sequential

Generally speaking, most of the drought patches are mainly distributed in the peak-cluster depressions, peak-cluster valleys, peak-forest valleys and karst plains near the watershed of all levels of river basins. For example, near the watershed between Hongshui River and Liujiang River in central Guangxi, that is, Masi in Xincheng to Maping in Xiangzhou, and the peaks and valleys and karst plains in Shilong area; Near the boundary ridge between Hongshui River and Yujiang River, that is, Yang Xiaoping in Xingbin District, LAM Raymond Valley and LAM Raymond Plain in wuxuan county Shiya to Lu Xin; The watershed between Hongshui River and Xijiang River in Guigang, Hengxian and Binyang. In addition, the watershed of main river tributaries is often the location of drought patches; There are also dry spots on both sides of deep valleys, such as Hongshui River and the middle and lower reaches of Liujiang River. Drought and water shortage is an important natural factor of ecological environment deterioration and poverty in karst arid areas, especially in central Guangxi, where land resources are abundant and water resources are unevenly distributed. Due to the above reasons, drought and water shortage are more severe.

(2) Comprehensive control measures

The development of agriculture and social economy in this area should fundamentally get rid of the trouble of drought and water shortage and realize the sustainable development of rural economy and society. We should start with the development, utilization, management, allocation, conservation and protection of water resources, and take comprehensive drought-resistant measures to improve the ability of drought prevention and control.

1. Basic principles

1) Rational distribution of water resources and national economy. Linking water resources development with national economic and social development, and implementing unified planning, unified deployment and unified management of groundwater, surface water and urban and rural water resources according to the requirements of water resources carrying capacity and ecological environment protection.

2) Develop water-saving agriculture and implement the strategy of sustainable utilization of water resources. Effective measures such as policy guidance, financial support and technical services should be taken to reduce water loss, improve irrigation system and irrigation methods, strengthen water management and adjust planting structure to achieve water-saving and efficient production.

3) Take the river basin as a unit, build a scientific and reasonable farmland water conservancy system according to local conditions, and optimize the allocation of water and soil resources. Carry out water conservancy projects of different scales, solve the imbalance of regional water and soil resources combination, scientifically utilize surface water, rationally develop groundwater, increase investment, strengthen the construction of drought-resistant water source projects, and develop farmland water supply infrastructure from multiple levels such as water conservancy hubs, storage ponds, well irrigation networks, and rainwater harvesting and irrigation saving projects.

4) Build a collaborative system of resources and environment. Improve the ecological environment of water source areas, control soil erosion, take large watersheds as the backbone and small watersheds as the unit, make unified planning of mountains, water, fields and forests, and gradually establish an ecological environment system that enhances the regulation function of water resources through engineering measures, biological measures and farming measures.

5) Follow the laws of nature and give full play to the potential of water-saving dry farming. Vigorously promote water-saving cultivation techniques in dry farming, alleviate the contradiction between supply and demand of agricultural water, build a reasonable development structure of dry farming, and minimize the impact of drought on agriculture in early farming areas.

2. Comprehensive control measures and countermeasures

1) Improve and transform water conservancy facilities to improve the comprehensive utilization efficiency of water conservancy projects. With the goal of water-saving irrigation, we should transform and build new water storage and diversion projects, improve the canal system of irrigation areas, improve the utilization rate of water, and rationally allocate limited water resources. Carry out comprehensive utilization of water conservancy facilities, improve the utilization efficiency of water resources and reduce the cost of agricultural irrigation water. Popularize and use new technologies and materials in the renovation and improvement of irrigation canal system to improve seepage control performance and reduce water loss; To develop hydropower resources, we should pay equal attention to hydropower, irrigation, flood control and shipping; When developing groundwater resources, it should be developed according to the water source conditions, urban and rural life, industrial production water supply source construction or aquaculture demand, so as to maximize the comprehensive benefits of water conservancy and improve the ability of drought resistance and waterlogging prevention. In areas lacking surface water, karst groundwater is rich in resources and good in water quality, which is suitable for irrigation and drinking. Underground rivers, karst springs, karst pools and other underground water outcrops, underground runoff and water storage structures can be combined with local conditions to develop appropriate groundwater resources and solve the problem of drought and water shortage in karst areas.

2) Make full use of the temporal and spatial distribution changes of water resources and implement the joint development of surface water and groundwater. The surface water system in karst plain is underdeveloped, and surface water and groundwater are transformed into each other through karst cracks and pipelines, and change with the seasons. Carry out joint development of surface water and groundwater, take pumping stations as far as possible before the surface water is cut off, and increase the recharge of groundwater aquifers through returning water from irrigation areas; By drilling wells or holes to get water, pumping underground regulating reservoirs will be built to solve the problem of regional inter-annual drought. This kind of karst area has the characteristics of strong shallow karst and good water storage permeability, and the karst aquifer has strong storage function. In the dry season when crops need water, over-exploitation of the middle and deep groundwater forms a regulated storage capacity, and after the rainy season, the underground storage capacity is restored through natural infiltration. In the development of groundwater, on the basis of excavating strip-shaped water storage structure, underground runoff zone or underground river with good water yield, a shallow well network matching with irrigation canals or cultivated land is built, and a small compound shallow well irrigation area with less investment, short cycle and low water intake cost is established. At the same time, it solves the water supply problems of scattered rural residents and large-scale farms. Taking the mainstream area of surface water system as an example, the average flow of Hongshui River for many years is 2 1.80 m3/h, which traverses the whole territory of Xingbin District. However, due to the influence of geology, topography and geomorphology, especially in karst rocky mountainous areas, the pumping irrigation function of Hongshui River has been greatly "shrunk", which makes it limited to the flat areas on both sides of the river, less than 1/5 of the whole area. Therefore, we should adjust measures to local conditions, rationally develop and utilize groundwater resources, establish field well irrigation network, and improve the development and utilization of groundwater resources.

3) Restore and rebuild the ecological environment of the water source, adjust the logistics mechanism of the water circulation system, reduce the loss of water resources, and enhance the water supply function of the system. Build forest ecosystem, improve water ecological environment, adjust forest species structure, increase the proportion of shelter forest and water source forest, adjust the process of transforming precipitation resources into surface water or groundwater resources through biological action, use the water conservation function of forest vegetation to alleviate uneven rainfall distribution in time, slow down the formation of rapid runoff time, reduce the loss of water resources, increase the water supply capacity of water resources system, and realize open source and throttling by combining engineering measures. According to the relevant research, surface runoff occurs when the rainfall of forestland in Guangxi reaches 8 mm, while that of forestland does not occur until the continuous rainfall reaches 22 mm, with a difference of14 mm. That is to say, in the process of precipitation, forestland stores more water 14 000m3 than forestland. Some of this water was evaporated and consumed, and returned to the atmosphere, while the rest remained in the same place, slowly seeping into the ground and becoming the recharge source of groundwater. When the local underground water is discharged from the ground, it will further replenish rivers, reservoirs and rice fields. Practice at home and abroad has proved that the forest coverage rate must reach more than 40% in order to keep the ecosystem in a virtuous circle. Therefore, on the premise of relatively stable planting area, we should adjust the large-scale steep slope upland meadow to forestry or high-quality pasture, create fast-growing and high-yield forests and excellent economic forests, introduce excellent pasture, and develop compound agriculture, forestry and animal husbandry. By restoring or rebuilding the ecological environment of water source, the system function and disaster resistance can be enhanced. Construct the structure of agriculture, forestry and animal husbandry adapted to severe seasonal drought, and promote the organic combination of agriculture, forestry and animal husbandry, which are interdependent and mutually reinforcing. Forest and grass vegetation can improve the ecosystem and enhance the availability of water resources, thus promoting the increase of crop yield and the development of animal husbandry. The increase of organic fertilizer will enhance the water retention of soil, form a strong drought resistance, and achieve the purpose of disaster prevention and reduction. Making the forest coverage rate reach more than 40% can not only adapt the agricultural structure to the climate characteristics of seasonal severe drought, but also improve the ecological environment, adjust the forest species structure and increase the proportion of shelter forests and water source forests. According to the principle of combining economic benefits with ecological benefits, afforestation tree species are selected and rationally allocated, such as: improved eucalyptus, slash pine, Pinus massoniana, Schima superba, camphor tree, Hainan peach tree, red cone fruit, Phoebe bournei, tung tree, black wattle tree, olive, chestnut, acacia Taiwan, sweet bamboo, bitter wood, jujube, kidney bean, Toona sinensis and goose skin fruit. Through effective measures, the benign cycle of the ecosystem is restored, and the ecological benefit index reaches about 95%, which is close to the optimal state. It has a good regulating effect on the movement of water, with precipitation increasing by 6.7% and evaporation decreasing by 3.2%. In addition, forests conserve water and reduce surface runoff, and only the water volume (conservative value) in Xingbin District increases 10× 108 m3.

4) Adjust the land use structure, build a good farmland ecosystem, and promote a virtuous circle of resource utilization and environmental improvement. The flat land and gentle sloping land in karst plain area are mostly cultivated land, which is mainly used for planting crops and sugarcane. According to the analysis of remote sensing, the utilization of cultivated land in Xingbin District and Binyang County accounts for 50.57% ~ 55.03% of the total land area, and the area of orchards and tea gardens is less than 0.5%. Increasing the area of fruit forest in plain platform and establishing farmland shelterbelt are beneficial to improve farmland ecosystem, microclimate and microcycle, reduce farmland water evaporation and loss, and enhance farmland system function and disaster resistance. The karst peak cluster area is dominated by forest and animal husbandry, surrounded by rocks and mountains, and the development of economic forests and woody feed and timber forests with good protective functions is dominated by animal husbandry; Planting in karst peak forest area is mainly dry farming, closing hillsides to facilitate afforestation, developing fruits, tung oil and woody feed, and developing pig industry and other aquaculture; In karst hilly area (buried karst area in Tertiary), forestry is mainly based on forest and animal husbandry, with fast-growing and high-yield timber forests and economic forests, and shelter forests are established in reservoir areas and river banks. Cattle and pigs are the main animal husbandry, and dry farming and economic planting are developed; The plain area should develop agriculture and animal husbandry, increase crop yield, and develop crop, pig and poultry breeding. Forestry production should focus on farmland shelterbelt, firewood forest and bank protection forest.

5) Adjust the planting structure and popularize water-saving dry farming, soil improvement and agronomic water-saving and drought-resistant technologies. According to the adaptability of crops to arid environment, predict the annual rainfall change and make full use of atmospheric moisture (rain, fog, dew, etc.). ), adjust the planting time of crops, and prevent the impact of drought on production through measures to avoid drought. For example, the Litang demonstration area implements paddy field rotation, combines farming and cultivation, and promotes the existing rice-vegetable rotation, multiple cropping of corn, melons and vegetables in dry land and dry land, and interplanting of fruits, peanuts and soybeans. The output value of green beans and bitter gourd planted in winter in the demonstration area is generally 3 000 ~ 5 000 yuan, with less pests and diseases, less pesticide consumption, less product residue, low production cost and good product quality. But autumn and winter and early spring are dry seasons in Guangxi, and water is the key to agricultural production. Therefore, building water-saving facilities, adopting water-saving production technology, developing water-saving agriculture and improving the utilization rate of water resources are conducive to giving full play to the functions of existing water conservancy facilities, reducing the water cost per unit output value and obtaining better benefits; Another example is the comprehensive drought resistance of sugarcane, that is, selecting improved varieties with drought resistance, high yield and high sugar content, planting early and managing early, changing spring seeds into winter seeds, prolonging the growth and development period and making full use of rainwater resources; Popularize agricultural water saving, control the ineffective loss of environmental water, and enhance the ability of soil water storage and water conservation. Covering with water, such as corn, vegetables, fruit trees and straw, can effectively control water evaporation and preserve water and fertilizer; Deep tillage, shallow planting in deep ditch, more organic fertilizer application, straw returning to the field, etc. Thicken topsoil and organic matter, improve soil structure, improve soil water holding capacity, and enhance water and fertilizer absorption and drought resistance; In sloping farmland, it is advocated to dig ditches along contour lines to reduce surface runoff, which can intercept a large number of surface slope flows, make water flow infiltrate in large quantities, increase soil moisture and groundwater recharge, effectively supplement soil evaporation and crop transpiration losses, and improve water and fertilizer conservation capacity.

6) Adjust the agricultural industrial structure and form a diversified agricultural economic system. In view of the seasonal, frequent and regional characteristics of drought in this area and its constraints on crop water demand. ① Accelerate the development of animal husbandry and increase the proportion of herbivorous livestock. This area is the main producing area of sugarcane, corn and peanuts, and there are a large number of agricultural and sideline products that can be used as high-quality feed, such as crop stalks, sugarcane tail leaves and peanut stalks. Moreover, there are abundant grassland and wasteland resources, so as to introduce and plant excellent pasture, improve pasture productivity, make grassland ecosystem produce efficient energy conversion and material circulation, promote the development of animal husbandry, establish high-quality and efficient breeding structure, and improve the proportion of animal husbandry in agricultural economy. (2) Strengthen the deep processing of agricultural products and vigorously support the food and feed processing industry, especially the processing industry with grain, fruits and vegetables as the main raw materials in the main grain producing areas. Based on local advantages, taking the development of agricultural products processing industry as a breakthrough, we should take the road of new agricultural industrialization and industrialization to promote agricultural efficiency, farmers' income and rural economic development. (3) To transform the tertiary industry system and develop modern rural service industry, it is necessary to build a good circulation network and facilities for agriculture. To build a circulation information network serving agriculture, one is to establish an internal economic information center to guide production and communicate production and sales; The second is to improve the service system of economic information market. It is necessary to continuously strengthen the construction of folk information networks and improve the service functions of the system; Third, create conditions to build an "information superhighway" to achieve fast, accurate, comprehensive, new and special results. Through the adjustment of industrial structure, the dependence of agricultural economy on high water consumption planting industry is decomposed, and the comprehensive drought and disaster prevention ability is formed.

7) Establish and improve the rural drought relief service system. Establish and improve the rural drought relief service network with the county-level drought relief service team as the leader, the township drought relief service team as the link and the village-level drought relief cooperation organization as the basis to provide professional and standardized services for farmers' drought relief. Adapt to the development of rural productive forces at this stage, provide mobile irrigation, drought-resistant equipment maintenance and rental services for farmers in marginal, remote, poor and difficult areas, demonstrate and popularize new drought-resistant and water-saving technologies, solve the problem of drinking water for people and livestock in arid areas, and solve the problem that farmers can't do it well. Provide technical support for drought resistance and disaster reduction.