Present situation and development of water-saving surface irrigation technology: surface irrigation technology is widely used at present, and the lack of water resources introduces water-saving concept into irrigation technology. Developing water-saving surface irrigation technology, improving the utilization rate of various water resources and improving the effective utilization rate of agricultural water are the main directions of current irrigation technology development. This paper analyzes the present situation of surface irrigation technology and irrigation measures in China, and probes into the development trend of new irrigation technology. Key words: water-saving irrigation technology: At present, surface irrigation is widely used in China. Traditional surface irrigation includes flood irrigation, grid irrigation, furrow irrigation and border irrigation. Due to uneven land, extensive irrigation management, imperfect irrigation facilities and serious waste of water resources. With the intensive transformation of land management scale, the application of laser leveling technology and the use of large agricultural machinery, surface irrigation has greatly improved irrigation efficiency and irrigation uniformity. In the design and management of surface irrigation, computer technology is a powerful tool to improve surface irrigation. In developed countries, some advanced surface irrigation technologies have also been widely used, such as field gate pipe system, horizontal border irrigation technology and cross-flow irrigation technology. The waste of water resources has been obviously improved. With the development of modern science and technology, the traditional surface irrigation technology has also undergone tremendous changes. Among them, precision surface irrigation technology has attracted worldwide attention and been applied in the field. In recent years, China has also paid more attention to surface irrigation technology, and set up a special project to track and study advanced surface irrigation technology. 1. Present situation of surface irrigation technology in China With the shortage of water resources, improving irrigation quality and surface irrigation technology is becoming the core part of agricultural water-saving technology. During the Ninth Five-Year Plan period, water-saving agricultural technology research and demonstration projects were included in the national science and technology research plan; Aiming at horizontal border irrigation technology and cross-flow irrigation technology, China Academy of Water Sciences has conducted in-depth research and achieved remarkable results. China Academy of Water Sciences introduced foreign advanced equipment and combined with foreign advanced technology to develop and produce flexible sluice pipes in the field and actively promote sluice pipe irrigation technology; China Academy of Water Sciences and the European Union jointly carried out project research to systematically improve the surface irrigation technology. Compared with foreign surface irrigation technology, there is still a big gap in China, and the research on related technologies needs to be further improved and strengthened. 2. Technical measures for surface irrigation Because of the large rural population, shortage of water resources, low economic level and low popularization of science and technology, it is difficult to popularize advanced irrigation technology in a large area. Therefore, for a long time to come, China must strengthen field engineering construction and actively promote water-saving surface irrigation technology. 2. 1 Leveling the land and designing reasonable irrigation technical parameters and furrow size are important measures to shorten irrigation time, save water and increase production, improve irrigation quality, irrigation labor efficiency and surface irrigation technology. In the field engineering transformation, leveling the land, widening the border into narrow border, dividing the long border into short border, and designing reasonable border flow and border ditch size can greatly improve irrigation efficiency and uniformity. China is a vast country with great differences in soil quality and topography, so it is impossible to adopt a unified standard. All localities should establish computer models according to the actual situation of local soil quality and topography, and determine reasonable irrigation technical parameters and silicon ditch size. 2.2 Improve drainage methods and develop intermittent irrigation. The traditional way of discharging water is once. Intermittent drainage technology was adopted in 1980s, which is regarded as a breakthrough in the development of surface irrigation technology. The main principle of intermittent water discharge is to use surge flow to promote the speed of water flow, increase the forward distance of water flow (about 1~3 times of the first water discharge), reduce the deep penetration of water flow, and make the utilization rate of field water reach 0.8~0.9. 2.3 Improve the wet mode of surface irrigation In the traditional wet irrigation mode, the proportion of non-tree-leaf soil evaporation to the total evaporation is very high, which reduces the utilization rate of field water. The local moist irrigation method makes up for this deficiency of the traditional method, improves the permeability of the soil in the root zone of crops, makes the root system grow deeper, improves the utilization rate of water storage in deep soil, and achieves the dual effects of increasing production and saving water. Practice has proved that alternate furrow irrigation or furrow irrigation can reduce the wetted area by 50%, increase the yield by 5%- 10% and save water by more than 30%. Sowing corn with water can save electricity by 90- 105 kW? H, saving water by 900 m3/h ㎡, increasing income by about 28% and increasing production by about 16%. 2.4 Compared with manual ditch drainage, the improved drainage facilities in the valley can improve the field water utilization rate by 5% ~ 10% by using the ground mobile sluice pipe (pipeline water delivery) or siphon pipe (open channel water delivery). However, these facilities have not been mass-produced in China and are still in the experimental stage. Therefore, it is necessary to step up the in-depth research on the materials of these processing technologies and equipment, and develop in the direction of popularization, production scale and technical standardization. 3. New water-saving technology 3. 1 Salt water irrigation technology Salt water irrigation mainly includes rotation irrigation and mixed irrigation with different water qualities. In addition, there is the technology of irrigation with groundwater, and the main principle is electroosmosis. Rotation irrigation is a method of alternating irrigation with salt and fresh water according to crop growth stage, crop species, salt tolerance and water resources distribution. If there is river water after rain, use fresh water and salt water in early season; Fresh water for weak salt-tolerant crops and salt water for strong salt-tolerant crops; Fresh water is used before sowing and seedling stage, and water is used in the middle and late stage of crops. Rotation irrigation can effectively play the role of salty and fresh water. Mixed irrigation is the use of two different irrigation water, including two kinds of mixed irrigation with different salinities, saline-alkali mixed irrigation (low salinity alkaline water) and saline-light mixed irrigation, in order to change its salt composition or reduce the total salinity of irrigation water. Mixed irrigation can not only increase the total amount of irrigation water, but also improve the quality of irrigation water, thus utilizing high salinity water or alkaline water that could not be used before. Austrian researchers developed an irrigation system based on electroosmosis principle. In this system, groundwater rises to the surface through various pores and soil capillaries, and purified water is released from the salt around the electrode and rises to the surface for crops. The equipment has two groups of electrodes: one group is a metal tube with a positive electrode, which is placed below the groundwater level; The other group is a conductive cupboard net as a negative electrode, which is buried in the roots of plants. According to the soil salt content and soil structure, when the power supply (2~ 12 V) is turned on, a DC electric field will be generated between the two poles, forming an electroosmosis effect. This irrigation system can be used for lawns with rich groundwater, sand-fixing plants and orchards in arid areas. 3.2 Sewage sprinkler irrigation technology Sewage sprinkler irrigation is an irrigation method combining agricultural water and sewage treatment, and it is also a sewage treatment method. Sewage should be treated (precipitation, screening and adding disinfectant) to remove solid pollutants before it can be used for sprinkler irrigation. Spraying sewage in the field, using crops, microorganisms and soil to decompose some components in sewage, so that some water can be reused after purification and infiltration, and some water can be evaporated into the atmosphere. Sewage irrigation is not suitable for vegetables. For other cash crops, it is best to use it only at the early stage of crop growth. The soil irrigated by sewage is loam sand, loam and sandy loam, and the amount of water should refer to the growing period and types of crops, such as late autumn, early spring and less irrigation at crop seedling stage. In order to avoid surface and underground runoff, sewage irrigation should be carried out in a large quota, and the irrigation intensity should be based on the principle of no surface runoff and no clay. The method of mixing sewage with clean water can be used to utilize the sewage that does not meet the irrigation water quality standard, and then sprinkler irrigation can be carried out after the mixed water quality reaches the standard. But the technical design is complex and can only be carried out under the guidance of experts. 3.3 The method of using moisture in the air for irrigation air moisture irrigation is to use relevant facilities to collect moisture in the air and collect it in a reservoir or directly supply it to plants. German researchers connected a cylinder with a solar absorption coating on its inner wall with several nozzles and buried these nozzles between the roots of plants. When the temperature drops at night, the air flowing from the cylinder into the nozzle condenses into dew and flows to the roots of plants. Peruvian researchers hang some large nylon nets vertically along the coast to collect fog, which condenses into water and then collects it in reservoirs to irrigate crops in coastal areas. In the desert, Chilean researchers use clouds to transform the desert. They used a huge frame to build a double-layer net made of polypropylene plastic to catch these clouds, which turned into water and then collected in a reservoir for desert irrigation. The above water-saving irrigation technologies are all new technologies developed in recent years, and various regions can choose appropriate methods according to local conditions. 4. Conclusion The lack of water resources makes "water saving" the core of irrigation technology, especially in China with a large population. Developing water-saving surface irrigation technology is an inevitable choice. However, the overall level of surface irrigation technology in China is backward, and there is still a long way to go to form an efficient water-saving irrigation system. In this case, the strong support of government leaders and the efforts of researchers from relevant departments are needed to ensure the smooth development of water-saving irrigation system. References: [1] Li Yi Nong. Study on farmland water and soil management for sustainable agricultural development [M]. Beijing: China Water Resources and Hydropower Press, 2000. [2] FAO. Guide for design and evaluation of surface irrigation system [M]. Beijing: China Agricultural Science and Technology Press, 1992. [3] Xu Di, Li Yi. Research and application of new water-saving irrigation technology in Tian Liang [M]. Beijing: China Agricultural Press, 2002. [4] Xu Di, Li Yi Nong. Technical system of precision surface irrigation and its research progress [J]. Journal of Hydraulic Engineering, 2007,38 (5): 529-535. 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