小流量微压滴灌技术应用基础研究
节水中心2009届博士研究生张林，在导师吴普特研究员、范兴科研究员的指导下，经过三年努力完成了小流量微压滴灌技术应用基础研究。
研究方向：节水灌溉新技术
摘 要
滴灌技术是当今世界上公认的最为节水高效的灌溉技术之一，但其昂贵的系统成本限制了技术的大面积推广和应用。为突破“昂贵”这一瓶颈，充分发挥滴灌技术的优越性，学者们提出了微压滴灌技术。微压滴灌技术为未来滴灌技术的发展开辟了一条新的途径。本文正是围绕目前微压滴灌技术存在的一些问题，对微压滴灌技术的应用问题作了大量的基础性研究。通过理论分析、试验研究和数值模拟相结合的研究方法，不仅研究了微压滴灌系统本身的问题，而且还将系统与土壤、作物结合起来，研究了系统对土壤水分运动及作物生长的影响，这样避免了孤立地就水论水，而是将水、土壤及作物三者结合起来进行系统研究。
针对原有微压滴灌系统存在的缺陷，以现代水力学理论为基础，通过试验研究，较为系统地分析了灌溉质量与压力、毛管铺设长度、毛管管径及灌水器设计流量等参数之间的定量关系，指出可通过同步降低滴灌系统的工作压力、适当增大管径、适当减小灌水器的设计流量及管道壁厚等四种技术途径来实现既降低系统成本又保证系统灌溉质量的双重目标，创新性地提出了小流量微压滴灌技术理念。
为了提高微压滴灌系统的设计精度，保证系统的灌溉质量，研究了滴灌系统技术参数对系统灌溉质量的影响，初步提出了微压滴灌系统中毛管适宜管径的确定方法，明确了微压滴灌系统的地形适应范围，并提出了微压条件下提高系统灌水均匀度的途径和方法，建立了均匀坡度下，综合考虑水力、制造及地形影响因子的滴灌系统流量偏差率计算公式，提出了微压滴灌系统灌水小区的设计方法。
为了进一步探讨小流量微压滴灌系统的可行性和科学性，同时，也为了科学地确定灌水器适宜流量，进行了小流量微压滴灌条件下土壤水分运移规律的试验研究，并根据非饱和土壤水动力学理论，建立了小流量微压滴灌条件下土壤水分运动的数学模型，利用试验数据对模型进行了验证，初步提出了滴灌系统中灌水器适宜流量的确定方法。
然而任何灌水技术都是以应用为目标的，灌水技术不同，其应用效果也不同。为了进一步验证小流量微压滴灌系统的可行性和应用效果，研究了小流量微压滴灌对作物生长的影响，结果证明小流量微压滴灌有利于作物的生长，可提高作物的产量和水分利用效率。
本文提出的小流量微压滴灌技术，不仅可以降低灌溉系统成本，而且还可以同步实现节水与增产的双重目标，具有广阔的应用前景。
关键词：小流量；微压；滴灌技术；流量偏差率；土壤水分
FUNDAMENTAL RESEARCH ON THE APPLICATION OF LOW FLOW AND MICRO-PRESSURE DRIP IRRIGATION TECHNOLOGY
ABSTACT
Drip irrigation is one of the most water saving and high efficiency irrigation technology in the world, but its high cost limits the large-area application of this technology. To break the "expensive" and give full play to the advantages of drip irrigation technology, micro-pressure drip irrigation technology has been put forward by scholars. Micro-pressure drip irrigation technology gives a new way to drip irrigation technology development for the future. Aiming at existing problems in micro-pressure drip irrigation technology, a lot of basic research was made in the thesis. Through theoretical analysis, experimental research and numerical simulation, this thesis studied not only in the micro-pressure drip irrigation system itself, but also the effects of micro-pressure drip irrigation to soil water movement and crop growth. Thus, the thesis didn’t only study irrigation on irrigation water; systematic research was made on the combination of water, soil and crop.
On the basis of modern hydraulic theory, the quantitative relationsship between irrigation quality and working pressure, lateral length of run, lateral diameter and designed emitter discharge was systematically analyzed by experiment. According to the theoretical and expermeantal analysis, the goals of reducing the system cost and ensuring irrigation quality can be achieved by simultaneously reducing working pressure of drip irrigation system, appropriately increasing pipe diameter, appropriately reducing designed emitter discharge and pipe wall thickness. And the concept of low flow micro-pressure drip irrigation technology was put forward innovatively.
In order to improve the design accuracy and ensure irrigation quality in the micro-pressure drip irrigation system, the impacts of drip irrigation system technical parameters on irrigation quality was studied. The method of determining the appropriate lateral diameter was initially established. The scope of the terrain was clarified for micro-pressure drip irrigation system. The measures of improving drip irrigation uniformity were proposed at the condition of micro-pressure. Taking account of the three deviation rates, a formula for computing the flow deviation rate was deduced on uniform slopes. And the method for designing irrigation unit of micro-pressure drip irrigation system was also put forward.
For proving the feasibility and scientificalness of low flow and micro-pressure drip irrigation system, and also scientifically determining the appropriate emitter discharge, the experiment of soil water movement was conducted under low flow drip irrigation. According to non-saturated soil water dynamics theory, the mathematical model for soil water movement was established. And it was verified by experimental data. At the same time, based on numerical simulation, the method of determining the appropriate emitter discharge was proposed for drip irrigation system.
However, any irrigation technologies should provide the crop required water to improve crop yield and water use efficiency. The effects of irrigation vary for the different irrigation technologies. Therefore, the effect of low flow drip irrigation to crop growth was studied in the thesis. The results show that, low flow and micro-pressure drip irrigation will be helpful to crop growth, and also improve crop yield and water use efficiency.
In a word, low flow and micro-pressure drip irrigation technology, not only can reduce system cost, but also achieve the dual goals of water-saving and increasing yield. Thus, it has broad application prospects.
KEY WORDS: low flow, micro-pressure, drip irrigation technology, flow deviation rate, soil moisture