微灌技术要素对土壤水分运动影响的数值模拟
发布时间：2018-11-28 20:42
【摘要】：滴灌作为一种高效的节水灌溉技术在新疆等干旱或半干旱地区得到广泛应用,为减小蒸发对土壤水盐运移的影响通常采用地埋的方式,即地下滴灌进行灌溉。微润灌则是以连续灌溉的方式通过地埋微润带将水分缓慢输送到植物根区的新型节水灌溉技术。数值模拟具有简便、快捷、灵活等特点,在给定的初始、边界条件下,可用于模拟各因素及其组合对土壤水流、溶质运移、热运移、植物根系吸水等方面的影响。国内的大多研究者往往只是证明该模拟值与实测值较为接近,在经验证模拟数据合理并近似于真实值后利用软件进行多因素、长时间的模拟试验研究尚不足。探明滴灌系统毛管布置方式和微润灌土壤水分运动规律,对与科学设计滴灌和微润灌系统,合理控制土壤盐分的运动具有重要意义。本文通过应用HYDRUS-2D软件,对不同灌水方式下土壤水分运动过程进行数值模拟,重点研究了地下滴灌灌水时间、滴头流量、灌水间隔等技术要素以及地下滴灌和微润灌两种不同灌水方式对水分运动的影响。得到如下主要结论:1、随灌水时间的增加,湿润峰垂直向上运移到达表层所用时间以幂函数趋势减小,垂直向下、水平方向运移距离均服从幂函数递增;不同方向湿润峰运移距离随滴头流量的增大呈幂函数增长;随灌水次数的增加呈对数函数增长。2、随滴头流量的增加三个方向上湿润峰运移距离随灌水时间增加的幂函数系数和指数均呈抛物线变化趋势,其中垂直向上的指数抛物线开口向下,其他方向的系数和指数抛物线均开口向上;且在滴头流量为1.5L/h处接近峰值。3、湿润面积随滴头流量和灌水时间增加分别呈线性增大,随灌水间隔增大呈指数下降,其中递增的滴头流量湿润面积曲线斜率大于灌水时间湿润面积曲线斜率;湿润面积与滴头流量和灌水时间的增大呈正比与灌水间隔的增大呈反比。4、随着滴头间距的增加水平方向上湿润区交汇的时间、湿润区交汇后形成“鞍部”消失所用的时间均随之增加;在滴头埋深附近,不同灌水时间、滴头流量、灌水间隔和滴头间距组合对土壤水分运动影响较大,在以滴头为中心40cm以外土壤内水分运动受以上四个因素组合的影响不明显。5、利用数值模拟对比地下滴灌和微润灌下水分运动发现,在地下滴灌带和微润带附近(小于5cm)的含水量和土水势均呈对称分布,之后地下滴灌受重力和其间歇灌溉的特点垂直向下的含水量和土水势变化快于其他方向,而微润灌仍以微润带为中心基本呈现对称分布。灌水量相同时,地下滴灌湿润体呈近似椭圆形,而微润灌湿润体近似圆形且湿润面积略大于地下滴灌。地下滴灌湿润土壤水分分布均匀度随灌水-间歇呈周期性减小-增大,微润灌水分分布均匀度随灌水逐渐增大且大于地下滴灌。
[Abstract]:As an efficient water-saving irrigation technique, drip irrigation is widely used in arid or semi-arid areas such as Xinjiang. In order to reduce the effect of evaporation on soil water and salt migration, underground drip irrigation is usually used to irrigate. Micro-irrigation is a new type of water-saving irrigation technology, which can transport water slowly to the plant root area by the way of continuous irrigation. Numerical simulation is simple, rapid and flexible. Under given initial and boundary conditions, it can be used to simulate the effects of various factors and combinations on soil water flow, solute migration, heat transport, water absorption of plant roots, and so on. Most researchers in China only prove that the simulated value is close to the measured value. After verifying that the simulated data is reasonable and approximate to the real value, the software is used to carry out many factors, and the long time simulation experiment is not enough. It is of great significance to find out the capillary arrangement of drip irrigation system and the law of soil moisture movement in micro-moisturizing irrigation, which is of great significance to scientifically design drip irrigation and micro-moisturizing irrigation system and to control the movement of soil salt reasonably. In this paper, the process of soil water movement under different irrigation modes was simulated by using HYDRUS-2D software, and the time and discharge of drip irrigation were studied. The effects of irrigation interval and two different irrigation methods, such as drip irrigation and micro-water irrigation, on water movement. The main conclusions are as follows: 1. With the increase of irrigation time, the time of vertical upward migration of wetting peak to the surface decreases with power function trend, and the distance of vertical downward and horizontal migration increases from power function; The migration distance of wetting peak in different directions increases by power function with the increase of emitter flow. With the increase of irrigation times, the power function coefficient and exponent of wetting peak migration distance increased with irrigation time in three directions, and the power function coefficient and exponent of wetting peak migration distance increased with the increase of emitter discharge. The index parabola in the vertical direction is open downward, and the coefficients and the index parabola in other directions are all open up. The wetting area increases linearly with the increase of emitter discharge and irrigation time, and decreases exponentially with the increase of irrigation interval. The slope of wetting area curve of increasing drip discharge is larger than that of irrigation time. The increase of wetting area is directly proportional to the increase of emitter discharge and irrigation time, and is inversely proportional to the increase of irrigation interval. The time of formation of "saddle" after the meeting of wet area increased. In the vicinity of emitter depth, different irrigation time, emitter discharge, irrigation interval and emitter spacing have great influence on soil moisture movement. The effects of the above four factors on the soil water movement outside the emitter 40cm were not obvious. 5. The results of numerical simulation were compared with those of the underground drip irrigation and the micro-moisturizing irrigation, and it was found that the soil moisture movement was not affected by the above four factors. The distribution of water content and soil water potential in the vicinity of the subsurface drip irrigation zone and the microwetting zone (less than 5cm) was symmetrical. After that, the vertical downward water content and soil water potential of the underground drip irrigation and its intermittent irrigation characteristics changed faster than those of other directions. However, the microirrigation still centered on the microwetting zone and presented a symmetrical distribution. When the irrigation amount is the same, the wetting body of underground drip irrigation is approximately elliptical, while the moist body of micro-moistening irrigation is round and the area of wetting is slightly larger than that of underground drip irrigation. The soil moisture distribution uniformity decreased and increased periodically with irrigation and intermittent irrigation, and the distribution uniformity of micro-moisture irrigation gradually increased with irrigation and was larger than that of underground drip irrigation.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S152.7;S275.5
本文编号：2364203
[Abstract]:As an efficient water-saving irrigation technique, drip irrigation is widely used in arid or semi-arid areas such as Xinjiang. In order to reduce the effect of evaporation on soil water and salt migration, underground drip irrigation is usually used to irrigate. Micro-irrigation is a new type of water-saving irrigation technology, which can transport water slowly to the plant root area by the way of continuous irrigation. Numerical simulation is simple, rapid and flexible. Under given initial and boundary conditions, it can be used to simulate the effects of various factors and combinations on soil water flow, solute migration, heat transport, water absorption of plant roots, and so on. Most researchers in China only prove that the simulated value is close to the measured value. After verifying that the simulated data is reasonable and approximate to the real value, the software is used to carry out many factors, and the long time simulation experiment is not enough. It is of great significance to find out the capillary arrangement of drip irrigation system and the law of soil moisture movement in micro-moisturizing irrigation, which is of great significance to scientifically design drip irrigation and micro-moisturizing irrigation system and to control the movement of soil salt reasonably. In this paper, the process of soil water movement under different irrigation modes was simulated by using HYDRUS-2D software, and the time and discharge of drip irrigation were studied. The effects of irrigation interval and two different irrigation methods, such as drip irrigation and micro-water irrigation, on water movement. The main conclusions are as follows: 1. With the increase of irrigation time, the time of vertical upward migration of wetting peak to the surface decreases with power function trend, and the distance of vertical downward and horizontal migration increases from power function; The migration distance of wetting peak in different directions increases by power function with the increase of emitter flow. With the increase of irrigation times, the power function coefficient and exponent of wetting peak migration distance increased with irrigation time in three directions, and the power function coefficient and exponent of wetting peak migration distance increased with the increase of emitter discharge. The index parabola in the vertical direction is open downward, and the coefficients and the index parabola in other directions are all open up. The wetting area increases linearly with the increase of emitter discharge and irrigation time, and decreases exponentially with the increase of irrigation interval. The slope of wetting area curve of increasing drip discharge is larger than that of irrigation time. The increase of wetting area is directly proportional to the increase of emitter discharge and irrigation time, and is inversely proportional to the increase of irrigation interval. The time of formation of "saddle" after the meeting of wet area increased. In the vicinity of emitter depth, different irrigation time, emitter discharge, irrigation interval and emitter spacing have great influence on soil moisture movement. The effects of the above four factors on the soil water movement outside the emitter 40cm were not obvious. 5. The results of numerical simulation were compared with those of the underground drip irrigation and the micro-moisturizing irrigation, and it was found that the soil moisture movement was not affected by the above four factors. The distribution of water content and soil water potential in the vicinity of the subsurface drip irrigation zone and the microwetting zone (less than 5cm) was symmetrical. After that, the vertical downward water content and soil water potential of the underground drip irrigation and its intermittent irrigation characteristics changed faster than those of other directions. However, the microirrigation still centered on the microwetting zone and presented a symmetrical distribution. When the irrigation amount is the same, the wetting body of underground drip irrigation is approximately elliptical, while the moist body of micro-moistening irrigation is round and the area of wetting is slightly larger than that of underground drip irrigation. The soil moisture distribution uniformity decreased and increased periodically with irrigation and intermittent irrigation, and the distribution uniformity of micro-moisture irrigation gradually increased with irrigation and was larger than that of underground drip irrigation.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S152.7;S275.5
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