用水平土柱与Green-Ampt模型方法测量土壤入渗性能的原理与误差

Principles and errors of measuring infiltrability with horizontal soil column and Green-Ampt model

土壤入渗是自然界水循环中的一个重要环节。研究提出了一种新的方法,根据水量/物质平衡原理和水平土柱中土壤剖面含水率分布所遵循的Green-Ampt模型中的活塞假定,测量和计算土壤入渗性能。用天然容重下的风干砂壤土,通过室内水平土柱试验,说明了获取数据的实验方法、过程,并利用提出的数学模型计算得到土壤入渗性能曲线。利用测量得到的土壤入渗性能回归计算得到的入渗水量分别与实际供水量和由土壤含水率的实际分布计算得到的入渗水量进行对比,得到相对误差分别为11.5%、15.89%,而实际供水量与由土壤含水率实际分布计算得到的水量之间的相对误差只有1.02%,说明了该方法的测量精度以及方法精度有进一步提高的可能性。该方法与传统的土壤入渗率测量方法相比,可以测量出土壤初始很高的入渗率,而且试验操作简单,省水,省时,为相关研究提供了有力的工具。

Infiltration is an important component of natural water circulation. A new method was advanced to experimentally measure and theoretically compute the soil infiltrability based on the water/mass balance and the assumption of Green-Ampt distribution of soil moisture content in the infiltrating horizontal soil column. A sandy loamy soil was used to illustrate the experimental method and procedures as well as the algorithms for estimating infiltrahility from the experimental data. Comparisons of the cumulative infiltrated water amount as computed with the estimated infiltrability with the total supplied water and that estimated from the actual changes in the moisture contents of the soil column indicate that the relative estimationerrors are 11.5% and 15.89% respectively, and the relative error between the actual supplied water volume and water derived from the actual water contents measured in the experiment is only 1.02%, which demonstrates a relatively high accuracy of the method and also the possibility to improve the accuracy of this method. The results show that the method can well conceptually represent the very high initial soil infiltrability compared with the conventional methods. This method is convenient for faster field determination of soil infiltrahility with much less water required. It will find its wide applications of future study in this direction.