Conversion of soil water retention and conductivity parameters from van Genuchten-Mualem to Groenevelt and Grant model

Author(s)

de Melo, Marina Luciana Abreu ^[1] ; de Jong van Lier, Quirijn ^[1] ; Armindo, Robson Andre ^[2]

Affiliation

^[1] Univ Sao Paulo, Ctr Nucl Energy Agr, Soil Phys Lab, POB 96, Piracicaba, SP - Brazil

^[2] Univ Fed Lavras, Dept Phys, BR-37200000 Lavras, MG - Brazil

• Document type: Journal article
• Source: SOIL RESEARCH; v. 59, n. 8 OCT 2021.
• Web of Science Citations: 0

Abstract

The van Genuchten-Mualem (VGM) model is used largely to represent the relative soil hydraulic conductivity and soil water retention functions {[}K-r(Theta) and Theta(h)]. Alternative equations proposed by Groenevelt and Grant (GRT) present advantages regarding mathematical versatility. Considering the VGM model cannot be analytically converted into the GRT model, this study empirically related parameters n and alpha (VGM) to parameters p and k (GRT). We used 90 value combinations of n and alpha and minimised the sum of squared differences between VGM and GRT models. Linear equations were fitted and validated using soil samples from the UNSODA database. A singular equation of p as a function of n was fitted, while a two-step procedure was required to correlate k and alpha. All fits resulted in very high precision (r >= 0.999) and accuracy (RMSD <= 0.025 m(3) m(-3)) for the water retention function and very high precision (r >= 0.994) for the hydraulic conductivity function. The accuracy for the K-r(Theta) function was high (RMSD <= 0.50) for 34 of the 40 tested soils. The derived empirical equations can be used to convert the equation parameters for Theta(h) regardless of soil type, and for K-r(Theta) with some restrictions upon parameter combinations. (AU)

• FAPESP's process: 18/12663-8 - Limiting hydraulic condition for drought stress in sugarcane
• Grantee: Marina Luciana Abreu de Melo
• Support Opportunities: Scholarships in Brazil - Master