灌溉优先流对裂隙分布密度、灌水强度及土壤湿度的响应机理  

Effects of Cracking Patterns and Antecedent Soil Water Content on Preferential Flow of Irrigated Water

作　　者：段凤仪 朱成立[1] 王策[1] 陈于 马靓 DUAN Fengyi;ZHU Chengli;WANG Ce;CHEN Yu;MA Liang(College of Agricultural Science and Engineering,Hohai University,Nanjing 211100,China;Jiangsu Rural Water Conservancy Science and Technology Development Center,Nanjing 210029,China)

机构地区：[1]河海大学农业科学与工程学院,南京211100 [2]江苏省农村水利科技发展中心,南京210029

出　　处：《灌溉排水学报》2023年第2期32-41,共10页Journal of Irrigation and Drainage

基　　金：国家自然科学基金青年项目(52109053);江苏省自然科学基金青年基金项目(BK20200523);江西省水利科学院开放研究基金项目(2021SKTR03);国家科技奖后备培育项目(20212AEI91011);江西省重点研发计划项目(20203BBGL73226)。

摘　　要：【目的】研究土壤初始含水率(土壤湿度)、裂隙分布密度及灌水强度对裂隙优先流强度的影响机理。【方法】构建基于水量平衡原理的优先流双域渗透模型,并通过染色示踪试验进行物理模拟及模型验证,基于模型数值模拟了裂隙分布密度、初始含水率和灌水强度三维因素旋转组合下的优先流特征。【结果】试验区的浅小型裂隙(裂隙平均宽度0.2 cm≤wc≤1.0 cm,平均深度0.5 cm≤d≤10 cm)与优先流的发育无直接联系,宽深型裂隙(裂隙平均宽度w_(c)≥2 cm,平均深度d≥50 cm)是产生裂隙优先流的主要原因;宽深型裂隙分布密度增大,基质流深度、染色面积率以及灌水均匀度增加;模型对裂隙优先流的模拟效果较好(R^(2)=0.951,P<0.01);模拟结果显示,裂隙深度很大程度上决定了优先流的最大入渗深度;接近土壤饱和导水率的灌水强度无法触发优先流,随着灌水强度增加,优先流程度和最大入渗深度增加,基质流深度和灌水均匀度降低;随着土壤初始含水率和裂隙分布密度增大,基质流深度和灌水均匀度增加,优先流程度降低。【结论】对于缩胀性较强、有机质量丰富的农田土壤,降低灌水强度、提高土壤初始含水率及裂隙分布密度能有效抑制裂隙优先流并提高灌水质量。【Objective】Macropores formed by physical and biological processes provide fast pathways for rainfall and irrigation water to bypass soil matrix.It has important implications not only for hydrological processes but also for biogeochemical processes.In this paper,we investigated the effect of cracking patterns and antecedent soil moisture content on preferential flow of irrigated water.【Method】Our study was based on numerical simulation and experiment.We first validated a dual-permeability model against a dye tracing experiment,and then applied it to elucidate how crack patterns,antecedent soil moisture content and irrigation intensity combined to modulate the formation and development of preferential flow of irrigated water in soil.【Result】Comparison with experimental results showed that the model is accurate for predicting preferential flow,with R^(2)=0.951 and P<0.01.Shallow small cracks with aperture in the range of 0.2~1.0 cm and in the depth of 0.5~10 cm had little impact on preferential flow,and large cracks with aperture more than 2 cm and expanding to the depth beyond 50 cm were the mechanisms underlying the formation and development of preferential flow.An increase in crack density enhanced both infiltration depth in soil matrix and soil water uniformity.Irrigation intensity less than saturated soil hydraulic conductivity did not trigger preferential flow.Increasing irrigation intensity increased infiltration depth in soil matrix and soil water uniformity in the soil.An increase in antecedent soil water content and cracking density increased water flow in soil matrix and soil water uniformity because of the reduced preferential flow.【Conclusion】In the fields with soil shrinkages and rich organic matters,reducing irrigation intensity and irrigating before soil water content drops below a certain level can reduce preferential flow and improve irrigation uniformity consequently.

关 键 词：裂隙优先流 双域渗透模型 裂隙分布密度 土壤初始含水率 灌水强度 

分 类 号：S152.7[农业科学—土壤学]