Estimation of Border-Strip Soil Hydraulic Parameters
Authors： Shobha Ram ; K. S. Hari Prasad ; Ajai Gairola ; M. K. Jose ; and M. K. Trivedi
Journal：Journal of Irrigation and Drainage Engineering
Volumes：2012.138(6)
Date：June 2012
Page number：493–502
Key words:Border-strip irrigation; Identifiability; Parameter estimation; Least-squares minimization; Sequential unconstrained
minimization technique.
Abstract：The inverse problem of determining soil hydraulic parameters(saturated hydraulic conductivity and water retention parameters)of border-strip irrigation from irrigation event data is analyzed. The inverse problem is solved using sequential unconstrained minimization technique. The forward problem involves the solution of coupled Saint-Venant’s equation governing overland flow and Richard’s equation governing subsurface flow. Saint-Venant’s equations are solved using the MacCormack scheme–based finite-difference method while Richard’s equation is solved using a mass conservative fully implicit finite-difference method. Field experiments are conducted on two border strips to obtain surface and subsurface irrigation data such as irrigation advance, recession, flow depth, and soil moisture content.The soil hydraulic parameters,i.e.,saturated hydraulic conductivity and soil retention parameters,are estimated by minimizing the deviations between the model-predicted and field-observed irrigation data. The results indicate that defining the objective function in terms of flow depths results in the optimization algorithm converging to the true values as compared to the use of irrigation advance data. Further, it is observed that underestimating the initial guess results in the least number of iterations for the optimization algorithm to converge to the true values. It is also observed that simultaneous estimation of all three soil hydraulic parameters is not possible even with the inclusion of subsurface moisture content data in the objective function.


《灌溉与排水工程杂志》刊登:边境地带土壤的水力参数估计
作者: Shobha Ram ; K. S. Hari Prasad ; Ajai Gairola ; M. K. Jose ; and M. K. Trivedi
刊物：灌溉与排水工程杂志
期刊号：2012, 138(6)
时间：2012年6月
页码：493–502
关键词：边境带灌溉，可识性，参数估计，最小二乘方法，连续的无约束极小化技术
摘要：分析了从灌溉数据中确定边境土壤灌溉的水力参数（饱和水力传导度和保水参数）。这些参数是通过连续的无约束极小化技术确定的。这个问题的解决是通过联立圣维南有关坡面流的方程以及理查德有关潜流的方程得到的。圣维南方程的求解是用基于有限差分法的MacCormack方法得到的，而理查德的方程求解时通过保守的全隐式差分法得到的。进行了田间试验获得了地表和地下灌溉数据如水流推进和后退、水流深度、土壤含水量。土壤水力参数，例如饱和水力传导和土壤保水参数，是通过最大限度的减少模型预测和现场观察到的灌溉数据之间偏差估计得到的。结果表明,定义了有关水流深度的目标函数的结果在收敛于真值方面,优于用水流推进得到的。另外，还发现低估了最初的猜测结果导致用较少的迭代使优化算法收敛到真值。还发现同时确定所有的土壤水力参数是不可能的，即使是在目标函数中包含了地下的水分含量数据。

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