(A) agricultural water-saving irrigation engineering technology types and characteristics

Water-saving irrigation engineering is the realization of water-saving irrigation basis, China from the 1950s and 1960s began the water-saving irrigation engineering technology testing, research and promotion, after more than 40 years of practice and exploration, in the water-saving irrigation planning, design, construction and other aspects of the increasingly sophisticated, such as the introduction of the "water-saving irrigation specifications", "sprinkler irrigation project design specifications", "micro-irrigation project design specifications", laid the foundation for the correct implementation of water-saving irrigation; at the same time, the development and production of water-saving irrigation equipment has formed a certain scale, the number of basic to meet the development of China's development of water-saving irrigation engineering technology. For the correct implementation of water-saving irrigation laid the foundation; at the same time, the development and production of water-saving irrigation equipment has formed a certain scale, in quantity basically meet the development of water-saving irrigation in China. Water-saving irrigation engineering technology mainly has the following kinds:

1. Channel seepage control engineering technology

Channel is the main means of water transfer in most of the irrigation area. The key to channel water transmission irrigation is to do a good job of channel seepage control. Channel seepage control irrigation technology using concrete sheathing, slurry stone lining, plastic film and other methods of seepage control treatment to reduce the water loss from the water source to the field to improve the efficiency of channel water transfer. Soil canal water transmission seepage loss is generally 20% to 40%, so that the utilization of water is greatly reduced, compared with the soil canal, channel seepage control can reduce seepage loss of 60% to 90% (Haisheng, 2003), channel seepage control technology is the key is to determine the appropriate seepage control materials and reasonable cross-section of the structural form.

Channel seepage control technology can reduce the permeability of the channel bed or establish impermeable protective layer to reduce leakage, so that the channel water loss is reduced to 5% to 10%. This technology is one of the earliest and most widely used water-saving technology, is currently the more ideal water transmission irrigation technology in large and medium-sized irrigation areas, its section form rectangular, trapezoidal and U-shaped. The materials used have developed from slurry masonry and precast panels to cast-in-place concrete. The canal water utilization coefficient of this irrigation technology can reach 70% to 80%, taking advantage of the difference in elevation of the terrain to flow water from the high place to the low place. But the channel seepage control only reduces the loss of water in the water transfer process, to further improve the water utilization rate, but also need to do the field water conservation project.

2. Low-pressure pipeline irrigation engineering technology

Low-pressure pipeline irrigation is referred to as pipe irrigation, is the use of machine pumps to extract river water, through the pump to provide a lower pressure through the plastic or concrete pipeline instead of the earth canal water transfer water directly to the field ditch, border irrigated fields, and then connected to the final level of the water hose to irrigate the crops in order to reduce the water in the process of transporting the seepage and evaporation losses. Pipe irrigation without hoses is called incomplete pipeline system, and those with hoses are called complete pipeline system. The latter saves more water than the former, but is more cumbersome to irrigate. Low-pressure pipeline water transfer technology can utilize up to 95% of water, in addition, it can effectively improve the speed of water transfer. Low-pressure pipeline water transfer technology has been popularized in China's northern well irrigation areas, but large-scale artesian irrigation areas are still in the pilot stage.

3. Sprinkler irrigation engineering technology

Sprinkler irrigation technology that is sprinkler irrigation technology, this irrigation technology is the use of water pumps or water sources of natural fallout pressurization, through the pipeline, sprinkler nozzle will be under pressure of water sprayed into the air, evenly dispersed to the field, the crop irrigation. Sprinkler irrigation technology is the main form of large-scale mechanization to solve the problem of water-saving irrigation of field crops. In the sprinkler irrigation machinery, pan (including the center pivot) type automatic sprinkler, hose reel automatic sprinkler and manually move the pipe sprinkler is the world's application of the three main models. Sprinkler irrigation is a mechanized high-efficiency water-saving irrigation technology, almost applicable to all field crops except rice, as well as vegetables, fruit trees, etc., on the terrain, soil and other conditions of adaptability, built in the undulating, soil permeability of the plot of land of the best economic efficiency. Compared with ground irrigation, sprinkler irrigation in addition to the main function of irrigation, but also can spray pesticides and fertilizers, create and improve the field microclimate, regulating the air, soil and crop temperature, humidity, can be used for crop frost and dry hot wind. Sprinkler irrigation for field crops can generally save 30% to 50% of water and increase yields by 10% to 30% (Haisheng, 2003). Sprinkler irrigation is also categorized as fixed, semi-fixed, and mobile, with the mobile type having the least investment, but with troublesome watering management. Planting a variety of crops in an area using sprinkler irrigation is not appropriate, and sprinkler irrigation by the wind and air humidity, the greater the impact of the design requirements are still relatively high, its equipment investment, high energy consumption, while the construction of large-scale equipment is more complex, the operation and maintenance of technical requirements of the operation of the operation of the management staff shall be specially trained.

4. Micro-irrigation engineering technology

Micro-irrigation is a new type of water irrigation technology, including drip irrigation, micro-sprinkler irrigation, spring irrigation and underground seepage irrigation, is a modernized, fine and efficient water-saving irrigation technology, with water saving, energy saving, adaptability and other characteristics, irrigation can be combined with the application of fertilizers at the same time, the irrigation efficiency can reach more than 90% (Zhu Li, 2002). Micro-irrigation has been developed from a few cash crops such as fruit trees and vegetables to row-seeded field crops.

Micro-irrigation technology is based on the plant's water requirements, through the piping system and installed in the end of the pipeline on the irrigator, the water and nutrients required for plant growth in a smaller flow rate uniformly and accurately delivered directly to the surface of the soil near the roots of the plant or in the soil layer. Compared with surface irrigation and sprinkler irrigation, micro-irrigation is localized and fine irrigation, with the highest degree of effective water utilization, saving about 50% to 60% of water and increasing yields by 20% to 30% compared with surface irrigation (Pan Yunming and Zhang Yongfeng, 2005), and saving 15% to 20% of water compared with sprinkler irrigation. However, the engineering investment of micro-irrigation is also high, which is called an expensive irrigation technology in foreign countries (Yang Shaojun, 1998), and this technology is also prone to pipe clogging. In order to support the high investment, micro-irrigation is generally used only for fruits, vegetables, flowers and other cash crops with high production value and high yield. Strictly speaking, micro-irrigation is less suitable for field food crops.

5. Membrane irrigation engineering technology

Membrane irrigation includes membrane irrigation and membrane irrigation. Membrane irrigation is on the basis of film cultivation, the previous side of the membrane side of the irrigation to membrane irrigation, water along the seedling release holes and the side of the membrane infiltration of crop irrigation. By adjusting the number of seepage holes at the beginning and end of the membrane border and the size of the holes to adjust the amount of water at the beginning and end of the border, you can get a relatively high degree of irrigation uniformity compared with the conventional ground irrigation method. Sub-membrane irrigation is to irrigate with drip irrigation water supply under the ground membrane, which is more water-saving than irrigation on the membrane. Membrane irrigation is easy to operate, easy to control the amount of water, can greatly reduce the deep soil leakage and evaporation losses, so can significantly improve the utilization of water. Mulch irrigation is suitable for the implementation of film planting of mesocosmic crops, compared with conventional furrow irrigation corn, cotton, can save 60% to 80% of the water, and have a significant increase in yield.

6. Ground irrigation engineering practical technology

Small border irrigation. Border irrigation is arable land after leveling, the use of border ridge will be divided into small pieces of the field for irrigation. Small border irrigation irrigation method for "long border to short border, wide border to narrow border, large border to small border" of the "three changes" border irrigation technology. The main points of small-border irrigation technology are to determine the reasonable length, width and flow rate of a single wide border. The width of the border field is 23m in the artesian irrigation area, and 1~2m in the machine well irrigation area. When the slope of the ground is 1/400-1/1000 (Hou Juping, 2002), the flow rate of single width is 2-4.51m3/s; the length of the border is 30-50m for artesian irrigation area, the longest length is not more than 80m, and about 30m for machine well and high-lift water lifting irrigation area. The height of the ridge is 0.2～0.3m, the width of the bottom is about 0.4m, and the ridge at the head of the ground and the ridge at the roadside can be widened and thickened appropriately.

Small block irrigation. In the northern application of block irrigation irrigation methods in most irrigation areas, generally in the block field on the use of large blocks of large water flood irrigation and large blocks of large water string irrigation, to block the field instead of the field water transmission canals and ditches, waste of irrigation water is quite large, not only the quality of irrigation is poor, but also affects the yield of the crop, resulting in soil swamping and salinization. In recent years, with the water shortage problem is prominent, widely used "big block to small block, wide block to narrow block and long block to short block" of the "three changes" irrigation technology, known as the small block irrigation, there are significant water saving and yield effect. Small block irrigation technology block field width is generally not greater than 5m, block field length should be in 5m or so, the best block field area less than 334m2, the maximum should not be more than 667m2, for no slope block irrigation, block field area, length and width can be compared with the slope of the block irrigation of a number of large. In general, the field area should not exceed 667m2, the length of the field should not be greater than 60m (Hou Juping, 2002), and the width should be less than 10m.

Long spit section irrigation. A long bed is divided into several short beds without horizontal ridges, using the ground longitudinal input ditch or plastic thin-walled hose, the irrigation water into the beds, and then from the bottom to the top or top to the bottom of the short beds sequentially section by section of the irrigation until all the short beds are irrigated until the irrigation method is known as the long beds segmented irrigation or long beds of short irrigation. If the long-border section irrigation uses the water conveyor ditch to convey water and irrigate, the first irrigation of the same water conveyor ditch should start from the end of the long-border short-border short-border to irrigate each short-border; the second irrigation should start from the beginning of the long-border long-border to irrigate the short-border short-border in each section from the top, and the water conveyor ditch can generally still plant crops.

7. Surge irrigation engineering technology

Surge irrigation is a major development of the ground furrow, border irrigation method, is the irrigation water intermittently according to a certain cycle to irrigation ditch (border) water supply, section by section to wet the soil, until the water flow into the irrigation ditch (border) until a water-saving new ground irrigation technology. Wave surge irrigation water supply is not continuous, its irrigation water flow is not once irrigation is advanced to the irrigation ditch (border) end, but the irrigation water in the first water supply into the irrigation ditch (border) up to a certain distance, pause the water supply, after a certain period of time and then continue to supply water, so that several times intermittent repeated to the irrigation ditch (border) water supply of the ground irrigation technology.