Estimation of Border-Strip Soil Hydraulic Parameters

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.

Estimation of Infiltration and Hydraulic Resistance in Furrow Irrigation, with Infiltration Dependent on Flow Depth

“…An alternative approach for estimating the parameters of flow-depth dependent infiltration models in surface irrigation is to use simulation optimization, as done by , Ram et al (2012), and Bautista and Wallender (1993). The first two studies dealt with border irrigation and modeled infiltration with the one-dimensional Richards equation.…”

Numerical and experimental investigations on aggradation and degradation in irrigation canals accounting for infiltration*

“…Numerous experimental and numerical studies were carried out for studying the sediment transport in irrigation canals (Brown et al ., 1988; Trout, 1996; Strelkoff & Bjorneberg, 2001; Strelkoff & Clemmens, 2005; Bjorneberg et al ., 2006; Ram et al ., 2006; Zhang et al ., 2012; Mailapalli et al ., 2013). Only few studies were either experimental or employed a simpler model for simulation of subsurface flow.…”

Development and testing of a large, transportable rainfall simulator for plot-scale runoff and parameter estimation

“…Some studies have focused on vertical variability of K s (Olyphant, 2003;Segal et al, 2008), but few have worked at the plot or hillslope scale. Ram et al (2012) performed experiments on 4 m wide border strips and used Typically, there is some compromise among the criteria as it is difficult to meet all of them. In addition to the primary objective of ease of portability, the choice was made to emphasize low cost, areal coverage, and reproducibility, with the added objective of being able to meet these criteria at at least two different rainfall intensities.…”