PDI model (Peter Durner and Iden model) is a water retention and hydraulic conductivitiy model considering both capillary and film flow, which covers the full range of water content from the saturatation to truly zero water content, instead of residual water content in the previous models, e.g. Van Genuchten model

More details of the PDI model can be found below:

Peters, A. ( 2013), Simple consistent models for water retention and hydraulic conductivity in the complete moisture range, Water Resour. Res., 49, 6765– 6780, doi:10.1002/wrcr.20548.

This pacakage includes:

(i) water retention function of PDI model, i.e. transfering water potenital into water content; (ii) parameter fitting to water rention characteristics/curves (iii) hydraulic conductivity calculation (both capillary and film flow) (iv) visulaizaotn of water retion fittings and hydraulic conductivity calculations