基于HYDRUS模型不同土壤有效水边界对沙壤土滴灌湿润体特性影响研究

发布时间：2018-03-22 21:07

本文选题：沙壤土　切入点：湿润比　出处：《西北农林科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：为解决西北地区水资源分布不均的现状,更好的保证作物节水高效,适应不同作物各个生育期根系的生长,采用不同的滴灌系统布置技术,形成不同的湿润体分布形式。以沙壤土(渭河陕西省杨凌段河滩砂壤土)滴灌为研究对象,采用室内试验和模型模拟试验相结合的研究方法,开展了基于HYDRUS模型不同土壤有效水边界对沙壤土滴灌湿润体特性影响研究,分析了滴灌水技术参数(滴头布置、灌水量、灌水流量)对湿润锋在水平、垂直方向的运移距离及不同边界界定条件下土壤有效湿润体形状、水分分布及随时间变化规律的影响规律,取得以下主要结果:(1)当灌水量相同时,大流量滴头湿润锋扩散迅速,小流量滴头扩散缓慢;灌水量相同时,不同流量滴头在滴灌结束后湿润体体积差异不大,但在土壤水分再分布过程中,小流量滴头相比大流量滴头扩散的范围更大,体积增大主要是垂直方向上水分运移的结果。当采用suffer软件和Auto-CAD软件对有效湿润体体积进行计算时,降低了有效湿润体计算的工作量,提高了计算精度;当有效湿润体边界层为田间持水量的60%~80%时,有利于植物吸收;按照60%田持为边界,滴头流量越小,经过再分布后土壤有效湿润体体积越大。(2)回归分析显示饱和区半径与流量关系呈指数关系,且随滴头流量增大而增大,可用于确定模型模拟的边界条件;利用实测数据对HYDRUS模型进行参数设定,对比分析湿润锋运移和含水率空间分布模拟值和实测值,其结果误差较小,具有较高精度。(3)采用HYDRUS软件模拟单点源和双点源滴灌不同设计工况下沙壤土入渗过程,对滴头流量、田持百分比(有效湿润体边界含水率值)、计划湿润比和滴灌结束后持续时间与实际有效湿润比进行相关性分析,均呈显著影响水平,其中田持百分比影响最大,计划湿润比和再分布时间次之,滴头流量影响最小;逐项因素梯度分析获得了滴头流量、计划湿润比、田持百分数边界以及再分布时间4种参数指标对实际有效湿润比的影响函数关系式;对于沙质土壤,以60%~80%田持含水率作为有效湿润边界,有效湿润体体积小于设计湿润体体积,而且有效湿润比还小于设计湿润比,对于合理确定沙壤土滴灌设计参数具有指导意义。
[Abstract]:In order to solve the present situation of uneven distribution of water resources in the northwest region, better ensure crop water saving and high efficiency, adapt to the roots of different crops in various growth stages of growth, the layout of different drip irrigation system, the formation of wetting body distribution in different forms. In sandy loam (Weihe Shaanxi section of Yangling river sand loam) using drip irrigation as the research object. Study on the method of laboratory test and simulation test was carried out by combining the HYDRUS model based on different soil water boundary effects on sandy soil wetting characteristics of drip irrigation, drip irrigation technical parameters (drip irrigation, irrigation layout, flow) of the wetting front in the horizontal, vertical migration distance and different boundary the soil moist body shape conditions, effects of water distribution and variation with time. The main results are as follows: (1) when the same irrigation amount, large flow drip wet Front rapid diffusion of small flow drip irrigation by slow diffusion; at the same time, different flow emitters in drip irrigation after the wetted volume had little difference, but the distribution of soil moisture in the process, the small flow range compared to large flow drip drip diffusion greater volume increase is mainly a result of vertical water movement. When the effective wetted volume was calculated using suffer software and Auto-CAD software, reduces the effective wetting calculation workload, the calculation accuracy is improved; when the effective wetted boundary layer for 60%~80% of field capacity, favorable for plant uptake; according to the 60% field capacity as the boundary, the emitter flow is small, after the distribution of soil wetted volume larger. (2) regression analysis showed an exponential relationship between saturated zone radius and flow, and it increases with the increase of dripper discharge, can be used to determine the model boundary conditions; and The HYDRUS model parameters by using the measured data set, comparative analysis of wetting front and water content spatial distribution simulation and measured values, the error is smaller, and has a high precision. (3) simulation of single and double point sources irrigation in different design conditions of soil soil infiltration in Xiasha by using HYDRUS software, the dripper discharge Tian, holding percentage (effective wetted boundary moisture content values), duration of wetting ratio and drip irrigation after wet ratio and the real effective correlation analysis showed a significant effect, which influences the percentage of maximum field capacity, wetting time and distribution, the emitter flow affect the minimum; one by one factor gradient the analysis of the emitter flow, wetting ratio, percentage of field capacity boundary and distribution time of the 4 parameters influence on the real effective wet ratio formula; for the sandy soil, the 60%~80% field to contain As the effective wetting boundary, the effective wetting volume is smaller than the designed wetting volume, and the effective wetting ratio is also less than the design wetting ratio. It has guiding significance for determining the design parameters of sandy loam soil 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】：2017
【分类号】：S275.6;S152.7

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