| Agriculture traditionally is a major water-consumer, with the agriculturalwater-consumption amounts up63.4%to the total water consumptionof ourcountry in2013. While the farmland irrigation has a rather low waterefficiency, only at0.523. So, the economical and efficient use of agriculturalwater is an effective approach to cope with the contradiction of demand andsupply of water resources, and of great importance to alleviate the well-knownwater crisis in China.General Office of the State Council of our country hasissued the―National Programme of Agricultural Water-conservation (for theyear2012-2020)‖in November2012, stressed water-saving irrigation as aprime strategy for the sustainable economic&social development and afundamental approach/measure for modern agriculture. The agriculturalwater-conservation has a long journey and heavy load.Border irrigation is the most common irrigation approach in our country,more popular in northen China such as Shanxi Province especially, and itscurrent water efficiency of application is still very inferior, promoting the water efficiency of application for border irrigation is vital to progress thewater-saving irrigation in our country. Based on testing and probing the currentwater efficiency of application for border irrigation in Shanxi province, thepresent dissertation adopted the methods of theoretical analysis and numericalcalculations coupling with field tests to systematically research the flowprocess the quality indices and the technical parameters optimization of borderirrigation/application, and demonstrated the results as follows:1. According to the nature of irrigation districts in Shanxi province, threeirrigation districts with different types of water sources were selected as thefield testing region. The current water efficiency situation of application andits affecting factors wereanalyzed with univariate statistics. And the resultsshowed that the main factors influencing the effective applicationefficiency arethe border-size, the designed-moistening-(layer)-depth, the quota ofapplication and the soil-texture; the water efficiency of application adds up inthe manner of positive correlation with the increase of the border framenumbers at a certain application quota and the same soil-texture,and with theincrease of designed depth in the limit of root-zone and/or moistening-layerprovided, their relationships fits in some logarithmic functions; the waterefficiency of application gradually decreases with the increase of single factorapplication quota, the relationship between them shows apparently logarithmic;and with the designed moistening depth provided and the border frame numberin a certain range, under same quota of application,the application efficiency for borders with soil texture as clay is larger than that for borders with loamsoil texture, while the water efficiency of application for borders with soiltexture as loam is apparently greater than that for borders with sandy texture.2. With the feature of the least square support vector machine probed, thepredicting models for water efficiency of application and for field roughnesswere formulated based on least square support vector machine. The waterefficiency of application model only need five accessible parameters as borderlength, border width, field slope, unit width flux, application quota to finishthe predicting process, its maximum relative error is11.98%, which verifiedthe corresponding model is feasible; By least square support vector machine,all the four proposed models for field roughness, which belonged to twoclasses, can be run to estimate the field roughness, the second class modelLSSVM-N-II has unified inputs and outputs without needing to make adistinction among different field types in particular, performed bettergenerality.3. With regard to the nature of border irrigation that the water flowprocessed along the field surface and infiltrated through the surface into thesoil during the application event, an border irrigation/application mathematicalmodel coupled zero-inertia module for surface flow with two-dimension soilwater movement equation has been formulated, Euler integration method andfinite element method are adopted to solve the zero-inertia model and Richardsequation respectively. With the coupling strategy of inner coupling, the zero-inertia model was efficiently iteratively coupled with the soil watermovement equation, the model can be used to numerically simulate the surfaceflow advance/recess procedures and soil water redistribution characteristics ofborder irrigation/application. By practically measuring the process and qualityindex of application/irrigation in three types (clay loam and sandy) borders, theproposed border irrigation water movement model was verified, the resultsshowed that the presented coupling model of zero-inertia surface flow and soilwater movement equation effectively simulated border irrigation surface flow&soil water movement process and application efficiency index, whichthereby confirmed the valid of the model.4. A multi-objective optimizing model for border irrigation technicalparameters was developed, based on the coupled module of zero-inertia andsoil water movement under border irrigation conditions,―mesh scanningsearch‖method was proposed to solve the model; the optimization results wereanalyzed and demonstrated that under the provided simulating conditions thewater efficiency of application and the distribution uniformity all indicated tovary along some convex-curve as the parameters(unit width flux, quota ofapplication and field slope) increase; the optimum solution/value ofapplication quota is0.0525-0.0675m (i.e. traditionally35-45m3per mu), that ofunit width flux is0.0035-0.0055m2/s, and that of field slope is0.003-0.005. |
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