东北典型黑土区土壤侵蚀过程顺坡起垄垄沟水力学特征分析
Analysis on the Hydraulic Characteristics of Longitudinal Ridges and Ditches in the Process of Soil Erosion in the Typical Black Soil Area of Northeast China
[目的]垄沟是垄作长缓坡耕地土壤侵蚀过程的重要汇流路径。本文通过室内人工降雨模拟实验,模拟不同雨强、坡度和垄作方式下垄作长缓坡耕地土壤侵蚀过程,提出作为主要汇流路径的垄沟的主要水力学参数和变量,从而为土壤侵蚀过程模拟提供技术支持。[方法]采用室内模拟降雨的方法,系统分析不同垄作方式、坡度、雨强等条件下垄沟的主要水力学参数和变量。采用正交试验设计,选取 3种典型降雨强度(30、50和 75mm/h)、3种裸地垄作方式(无垄、顺坡宽垄和顺坡窄垄)、2种漫川漫岗区地表坡度(3和 5°)进行全面试验。曼宁糙率系数可反应垄沟的粗糙程度对水流的阻滞作用。[结果]不同垄作方式下,坡面径流量和侵蚀量整体为窄垄>宽垄>无垄,并与坡度和雨强呈现线性正相关。在雨强和坡度较小时,三者坡面侵蚀量差异不显著;而随着雨强的增大,侵蚀量高低呈现窄垄>宽垄>无垄。水力半径随雨强和坡度的变化曲线呈对数关系;宽垄水力半径比窄垄高 8.4～11.6%,平均为 10.0%。在坡度和雨强相同的情况下,宽垄垄沟糙率n1 明显高于窄垄垄沟糙率n2,并且在坡度上升后,n1 相较于n2 在坡度上升后减小幅度更小。宽垄垄作方式相较于窄垄对坡面径流的阻滞作用更大,可降低坡面流速,减少径流对坡面的侵蚀冲刷,更适用于东北典型黑土区。研究测定垄沟糙率n变化于 0.082～0.229之间,平均为 0.145.SWAT模型建议垄作裸露坡面n取值范围为 0.06～0.12,平均为 0.09,明显低于本试验测量值。[结论]东北典型黑土区坡度较缓,汇流过程中垄沟内径流深度较浅,使得垄沟糙率有所增加。在进行本区坡面土壤侵蚀过程模拟时,不宜直接使用国外已有模型参数值,应结合本区自然地理环境和耕作特征,根据试验数据对模型系数进行修订。本文结合实际情况对其重新率定,其结果可为本区水土保持模拟提供依据。[讨论]顺坡垄作的垄沟糙率n主要受降雨强度、雨型、坡度等因素的影响,今后应进一步深入研究垄作方式、雨强、坡度对坡面径流流速的影响和坡面侵蚀的问题,为深入分析和解决东北黑土区土壤侵蚀问题,提供理论依据和数据支撑。
[Objective]Ridge and furrow is an important confluence path in soil erosion process of long and gentle slope farmland.It is very important to understand the hydraulic characteristics of ridge and furrow for simulating the soil erosion process of slope farmland in typical black soil region of Northeast China.[Method]The main hydraulic parameters and variables of ridge and furrow under different ridge cultivation methods,slope and rainfall intensity were systematically analyzed by using indoor rainfall simulation method.[Result]The results showed that under different ridge planting patterns,the runoff and erosion amount were narrow ridge>wide ridge>no ridge,and showed linear positive correlation with slope and rainfall intensity.The variation curve of hydraulic radius with rainfall intensity and slope is logarithmic;The hydraulic radius of wide ridge is 8.4-11.6%higher than that of narrow ridge,with an average of 10.0%.Under the same slope and rainfall intensity,the roughness of wide ridge is higher than that of narrow ridge;Moreover,with the increase of slope,the decrease of the roughness of wide ridge is weaker than that of narrow ridge.[Conclusion]There is a significant difference between the recommended values of slope roughness in the existing soil erosion models and the observed values in this experiment.Therefore,it is necessary to re calibrate the soil erosion process of long and gentle slope cultivated land under ridge cultivation in this area.
李坤衡;焦剑;秦伟;殷哲;
中国水利水电科学研究院,北京市 100048##辽宁工程技术大学 环境科学与工程学院,辽宁阜新 123000;中国水利水电科学研究院,北京市 100048;中国水利水电科学研究院,北京市 100048;中国水利水电科学研究院,北京市 100048;
Northeast black soil Area Soil erosion Manning model Hydraulic radius Roughness2
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