水平微润灌湿润体HYDRUS-2D模拟及其影响因素分析

为探索土壤质地、初始含水率、压力水头和埋深对水平微润灌土壤湿润体特性的影响机理,利用试验数据验证了水平微润灌HYDRUS-2 D模拟结果的可靠性,模拟值与实测值非常吻合。在此基础上,模拟研究了3种土壤质地(砂壤土、壤土、粉壤土)以及壤土中不同初始含水率(0.085、0.106、0.130 cm~3/cm~3)、压力水头(0.6、1.2、1.8 m)和埋深(20、30、40 cm)条件下土壤湿润体动态变化规律。结果表明:土壤湿润锋运移距离皆符合垂直向下水平方向垂直向上的规律,湿润体在形状上差异不大,土壤含水率等值线均为近似"同心圆";土壤质地对湿润体特性有显著影响,土壤质地越黏重,湿润锋运移速率越慢,湿润体体积越小,土壤含水率等值线越密集,其"圆心"越靠近微润管,灌水结束时,壤土和砂壤土湿润体体积分别是粉壤土的1.3倍和2.5倍;在确定的土壤质地条件下,初始含水率和压力水头对湿润体特性有较大影响,湿润锋运移距离及湿润体体积均随土壤初始含水率、压力水头的增大而增大,初始含水率为0.106和0.130 cm~3/cm~3的湿润体体积分别是0.085 cm~3/cm~3的1.2倍和1.5倍,压力水头为1.2和1.8 m的湿润体体积分别是0.6 m的1.6倍和2.2倍;微润管埋深对湿润体分布位置有显著影响,埋深较浅时,湿润锋容易到达地表,埋深较深时,土壤湿润体随埋深下移而同步下移。

HYDRUS-2D simulation of soil wetting pattern with horizontal moistube-irrigation and analysis of its influencing factors

Abstract: In order to investigate the influence mechanism of soil texture, initial water content, pressure head and buried depth on soil wetting characteristics of horizontal moistube irrigation, a mathematical model of soil water movement under horizontal moistube irrigation was established based on HYDRUS-2D model, and the relationship between the specific flow rate and pressure head was determined. We compared HYDRUS-2D simulations of horizontal moistube irrigation with experimental data. The HYDRUS-2D predictions of the cumulative infiltration, wetting front distance and water content distribution were found to be in very good agreement with the data. The results supported the use of HYDRUS-2D as a tool for investigating and designing moistube irrigation management practices. In the case of different soil textures (sandy loam soil, loam soil and silty loam soil) and the same soil texture (loam soil) with different initial moisture contents (0.085, 0.106, 0.130 cm3/cm3), pressure water heads (0.6, 1.2, 1.8 m) and buried depths (20, 30, 40 cm), the dynamic change of wetted soil characteristics was simulated by HYDRUS-2D software. The results showed that: The transport distance of soil wetting front in 3 directions is vertical downward > horizontal direction > vertical upward, the influencing factors (soil texture, initial water content, pressure head and buried depth) have small impact on the shape of wetted pattern, and the contour of soil water content is approximately "concentric circle". Under the same soil initial water content, pressure head and buried depth, the soil texture has a significant influence on the wetted soil characteristics. When the soil texture is heavier, the wetting front moves slower, the difference of wetting front distance is smaller in each direction, the wetted soil volume is smaller, the soil water content near the moistube is higher, the contour of soil water content is more intensive, and the "center of the circle" is closer to the moistube. At the end of the irrigation, wetted soil volumes for loam soil and sandy loam soil are respectively 1.3 and 2.5 times that for silty loam soil. At the moistube wall, soil water content of 3 kinds of soils (sandy loam soil, loam soil and silty loam soil) is 0.276, 0.359 and 0.406 cm3/cm3 respectively. Under the same soil texture, pressure head and buried depth, the soil initial water content has a great influence on the wetted soil characteristics, and the distance of wetting front and the volume of wetted soil are positively correlated with soil initial water content, and increase with the increase of the soil initial water content. At the end of the irrigation, wetted soil volumes for soil initial water content of 0.106 and 0.130 cm3/cm3 are respectively 1.3 and 2.5 times that for 0.085 cm3/cm3. Under the same soil texture, soil initial water content and buried depth, the pressure head has a great influence on the wetted soil characteristics, and the distance of wetting front and the volume of wetted soil are positively correlated with pressure head, and increase with the increase of the pressure head. At the end of the irrigation, wetted soil volumes for pressure head of 1.2 and 1.8 m are respectively 1.6 and 2.2 times that for 0.6 m. At the moistube wall, soil water content of pressure heads (0.6, 1.2 and 1.8 m) is 0.323, 0.359 and 0.380 cm3/cm3 respectively. The buried depth of the moistube has a significant effect on the distribution position of the wetted soil. When the buried depth is shallow, the wetting front is easy to reach the ground surface. When the moistube is buried deeper, the wetted soil will move down synchronously with the buried depth.