Document Type : Research Paper

Authors

• Meysam Ramezani
• Shokoofeh Salehi
• Abdolmajid Liaghat
• Mohammad Ali Gholami Sefidkouhi

Water Engineering, SANRU

Abstract

Soil water retention curve (SWRC) is necessary for many studies, such as unsaturated hydraulic conductivity and solute transport in porous media. However, its direct measurement is time consuming and expensive. In this study, an optimization method was developed in order to estimate soil water retention curve from limited measured points, such as water contents at field capacity and permanent wilting point. The main advantage of this method is that it is database independent. Three data sets including 156 soil samples from Belgium and Iran were used. Using van-Genuchten water retention model with restriction m=1-1/n and assuming residual water content to be equal to zero, vG model parameters such as  and  were optimized using two measured points and, consequently, SWRC was estimated (proposed method).  Bulk density was used in order to estimate porosity in this method. In addition to the proposed method, ROSETTA model was applied to estimate vG model parameters and SWRC from sand, silt, and clay contents, bulk density, and water contents at field capacity and permanent wilting point. The MR, RMSE and AIC values for the proposed method were -0.00084, 0.031 and -8636 (cm³.cm^-3) and for ROSETTA method were -0.037, 0.051 and -7327 (cm³.cm^-3), respectively. Comparison of estimated SWRC using the proposed and ROSETTA method showed that the developed optimization method estimated SWRC more accurately than ROSETTA  model.

Keywords

• Field capacity
• Optimization method
• Permanent wilting point
• ROSETTA model
• van-Genuchten model