Naveed, Muhammad4; Møldrup, Per5; Tuller, Markus6; Ferre, T. P. A.7; Kawamoto, Ken8; Komatsu, Toshiko9; de Jonge, Lis Wollesen4
1 Section of Biology and Environmental Science, The Faculty of Engineering and Science, Aalborg University, VBN2 Department of Chemistry and Bioscience, The Faculty of Engineering and Science, Aalborg University, VBN3 The Faculty of Engineering and Science (ENG), Aalborg University, VBN4 Institut for Agroøkologi - Jordfysik og Hydropedologi5 Department of Civil Engineering, The Faculty of Engineering and Science, Aalborg University, VBN6 Univ Arizona, Dept Soil Water & Environm Sci, Tucson, AZ USA7 Univ Arizona, Dep Hydrol & Water Resources, Tucson, AZ USA8 Saitama Univ, Dep Civil & Environm Engn, Sakura Ku, Saitama 3388570, Japan9 Saitama Univ, Inst Environm Sci & Technol, Sakura Ku, Saitama 3388570, Japan
Modeling water distribution and flow in partially saturated soils requires knowledge of the soil water characteristic (SWC). However, measurement of the SWC is challenging and time-consuming and, in some cases, not feasible. This study introduces two predictive models (F-w-model and A(w)-model) for the SWC, derived from readily available soil properties such as texture and bulk density. A total of 46 undisturbed soils from different horizons at 15 locations across Denmark were used for model evaluation. The F-w-model predicts the volumetric water content as a function of volumetric fines content (organic matter and clay). It performed reasonably well for the dry-end of SWC (above a pF value of 2.0; pF = log(vertical bar Psi vertical bar), where Psi is the matric potential in cm), but did not do as well closer to saturated conditions. The A(w)-model predicts the volumetric water content as a function of volumetric content of different particle size fractions (organic matter, clay, silt, and fine and coarse sands). The volumetric content of a particular soil particle size fraction was considered if it contributed to the pore size fraction still occupied with water at the given pF value. Hereby, the A(w)-model implicitly assumes that a given particle size fraction creates an analogue pore size fraction and further this pore size fraction filled with water is corresponding to a certain pF value according to the well-known capillary rise equation. The A(w)-model was found to be quite robust, and it performed exceptionally well for pF values ranging from 0.4 to 4.2 for different soil types. For prediction of the continuous SWC, it is recommended to parameterize the van Genuchten model based on the SWC data points predicted by the A(w)-model.
Soil Science Society of America. Journal, 2012, Vol 76, Issue 6, p. 1946-1956