Assessment of Soil Hydraulic Characteristics in Surface Irrigation via a Three-Term Infiltration Equation

Abstract This study investigates the integration of the three-term approximation of the analytical formulation of the Haverkamp infiltration equation into the Lewis-Milne framework to develop an advanced function for surface irrigation. The inverse solution of the equation allows for the estimation of fundamental soil hydraulic characteristics, specifically sorptivity ( S ) and saturated hydraulic conductivity $$(K_s),$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:msub> <mml:mi>K</mml:mi> <mml:mi>s</mml:mi> </mml:msub> <mml:mo>)</mml:mo> <mml:mo>,</mml:mo> </mml:mrow> </mml:math> provided that the advance time at two points along the furrow length is known (two-point method). The implementation of the method across various datasets has shown that the anticipated values of S and $$K_s$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>K</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:math> closely align with those predicted by the recent approach of Kargas and Mindrinos ( Irrigation and Drainage , 1–15, 2024), as well as by the method employed by Ebrahimian et al. ( Irrigation Science , 28 , 479–488, 2010) for the S values. If just the advance time at the furrow’s end is known, the values of S and $$K_s$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>K</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:math> can be determined using the one-point method, assuming that the power advance exponent is 0.5. The findings showed that the one-point method’s average value for the parameter S is higher than that of the two-point method’s, while the parameter $$K_s$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>K</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:math> shows the reverse trend.