间接地下滴灌土壤湿润体特征参数

Characteristic parameters of soil wetted volume under indirect subsurface drip irrigation

该文将恒定水头钻孔积水入渗求解土壤饱和导水率的稳态原理用于定量化求解间接地下滴灌技术中与任意导水装置尺寸相匹配的滴头流量,并以计算的技术参数为基础,研究了间接地下滴灌水分运移过程中的土壤湿润体特征参数。研究结果表明,用于描述恒定水头钻孔积水入渗法求解土壤饱和导水率的稳态模型能够较好地设计与不同类型土壤和导水装置尺寸相匹配的适宜滴头流量。间接地下滴灌灌水过程中,从零开始逐渐增大并趋于稳定的积水深度加速了水分在垂直方向的运移,缩小了横向湿润距离和垂向湿润距离之间的差异,但变化的积水深度对湿润锋在垂直方向向上和向下的运移速率影响不大,使湿润体形状表现为扁率不断减小的椭球体,且椭球体对称轴分布在靠近导水装置底部的位置。湿润锋最大湿润距离和湿润体体积是灌水时间的函数,湿润体内平均体积含水率增量与灌水时间关系不大,保持为一定值。湿润体体积和湿润体内平均体积含水率增量不仅与土壤类型有关,还与导水装置参数和滴头流量的不同组合有关。

The steady-state principle of constant-head well permeameter,which was used to calculate the field-saturated hydraulic conductivity,was applied to quantify the suitable emitter discharge rate for indirect subsurface drip irrigation under different water-conducting device specification conditions in this text.Using the calculated emitter discharge rate to supply water,characteristic parameters of wetted soil volume were studied during the water movement process. Results indicated that the steady-state model of constant-head well permeameter could be used to design the emitter discharge rate for different water-conducting device specifications and soil types.During the infiltration process of indirect subsurface drip irrigation,the ponded water depth changed from zero to a constant and accelerated the water movement in the vertical direction,which reduced the discrepancy of wetted distance in lateral direction and vertical direction,while the changed water depth had small influence on the wetting front movement in vertical direction to upward and downward.The shape of wetted soil zone was spheroid,and its symmetry axis lied near the bottom of the water conducting device.The maximum wetted distance and volume of wetted soil zone were the function of irrigation time.The increment of average volumetric water content in the wetted zone had no relationship with irrigation time,and kept a constant during the whole irrigation process.The volume of wetted soil zone and the increment of average volumetric water content in wetted zone had relationship not only with soil types,but also with the combination between water conducting device parameters and emitter discharge.