A new and simple water retention model for root-permeated soils

Vegetation can affect soil hydrology not only through evapotranspiration but also through changes in soil water retention curve (SWRC). Models that are able to predict root-induced change in SWRC are limited. Such models often contain many empirical parameters that are not easy to be obtained and calibrated. This letter proposes a new and simple model with only one root parameter, namely root volume ratio R_v, needed for predicting the SWRC of a root-permeated soil. The new model considers void ratio change through volume reduction of air void of soil due to the presence of roots. The modified void ratio of a root-permeated soil is then fed into a void-ratio-dependent SWRC model to predict any resultant change in SWRC. The performance of this new model is validated against three case studies. Good agreement between measurements and predictions is obtained, with discrepancies of degree of saturation <13% for a given suction.