Study On Sprinkler Irrigation Uniformity Characteritics And Optimization Of Pipe Network System Of Artificial Forage In The Arid Area And Semi-arid Area

This thesis studied on the sprinkler irrigation uniformity characteristics and network system optimization of cultured forage grass irrigation in the Mu Us Desert of Arid Area and Semi-arid AreaFollowing main results and conclusions are obtained:1. The root depth of 3-year- old alfalfa can reach 100 centimeters in the soil, but most roots stand underground 0-50 centimeters in the Mu Us Desert2. In the Mu Us desert, either vertical distributions of soil moisture isogram before irrigation or vertical distributions of soil moisture isogram after irrigation shows obviously vertical-layered character. When the irrigation is finished 24 hours later, there is little correlation between vertical distributions of soil moisture isogram before irrigation and vertical distributions of soil moisture isogram after irrigation. All of probability distribution of soil water content before irrigation are left-skewed distribution, but some of probability distribution of soil water content after irrigation is left-skewed distribution, some is right-skewed distribution or normal distribution. The distributed pattern shows different between the probability distribution of water depth of rain gauge and that of soil moisture in horizontal section of different depth. There is close correlation between the distribution of water depth of rain gauge and that of soil moisture in horizontal section, but the correlation debases as the horizontal section turns deeper. Also after irrigation close correlation occurs between the distribution of soil moisture of layers bordering upon each other, but which reduces with space of different layers being larger. 3. Variation degree of soil moisture before or after irrigation in experimental section behaves weak variation. And the absolute variation degree of soil moisture after irrigation in experimental section increases visibly, by contraries the relative variation degree of soil moisture after irrigation in experimental section decreases clearly. There is spatial variation characteristics in the spatial distribution of soil moisture underground 0-50 centimeters in the Mu Us Desert, and the variation degree of soil moisture distribution after irrigation is obviously higher than that before irrigation.4. When the water depth of irrigation reaches between12 and 40 millimeters, the sprinkling uniformity degree keeps from 60.34 percent to 96.20 percent. The uniformity coefficients of soil water content in the different layers underground 0-50 centimeters is evidently larger than that of rain gauge.5. The concept of effective wetness soil layer is put forward in the thesis, also the definition formula of the uniformity coefficients of soil water content of effective wetness soil layer is made. In the depth of forage grass roots, underground 0-50 centimeters, S_u (the uniformity coefficients of soil water content of effective wetness soil layer) is clearly higher than C_u (the corresponding uniformity coefficients of rain gauge). There is linear correlation to a large extent between the uniformity coefficients of soil water content of effective wetness soil layer and combination distance, based on which the linear regression equation between the uniformity coefficients of soil water content of effective wetness soil layer and sprinkler's combination distance is obtained.6. S_u, the uniformity coefficients of soil water content of effective wetness soil layer, is introduced into network optimization of sprinkling system and the nonlinear programming model of network optimization of sprinkling system is also established. A practical sprinkler irrigation engineering is optimized by LINGO9.0, as a result, a satisfactory solution of network optimization of sprinkling system is worked out.