Capillary saturation function of van Genuchten for unimodal or bimodal pore space distributions.
Sat_old(suc, par.shp, modality = c("uni"), suc.negativ = TRUE)Suction/pressure heads. Negative if suc.negativ = TRUE
named parameter in list or vector
pore size distribution ('uni' or 'bi')
set TRUE if suction/pressure heads are negative and FALSE if positive
additional for bimodal (modality == 'bi'): w2 [-]: weigthing between pore space distribution alfa2 [1/L]: van Genuchten parameter alfa for second pore space distribution n2 [-]: van Genuchten parameter n for second pore space distribution
Van Genuchten, M. T. (1980). A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil science society of America journal, 44(5), 892-898.
Durner, W. (1994). Hydraulic conductivity estimation for soils with heterogeneous pore structure. Water Resources Research, 30(2), 211-223.