Groundwater

Sub-surface drainage out of the soil column as an exponential function of water table depth, modulated by an impermeable-fraction reduction in frozen soils, following Oleson et al. (2010, CLM Tech Note Ch. 5) Eqs. 5.140 (drainage) and 5.141 (impermeable fraction). q_drai = (1 - f_imp) * q_drai_max * exp(-f_drai * z_v); f_imp = max((exp(-α(1 - f_ice_weighted)) - exp(-α)) / (1 - exp(-α)), 0). Migrated from UrbanCanopy.jl@9200edd4 src/hydrology.jl:698 (`GroundwaterDrainage` @component). Observed-only: both inputs are parameters and both outputs are given by single algebraic equations.

Water table depth z_v as a function of unconfined-aquifer water storage W_a and the depth of the bottom soil interface z_h_bottom. Implements Oleson et al. (2010) CLM Tech Note Eq. 5.146 (p. 143) with hard clamps at z_v_min = 0.05 m and z_v_max = 80 m. Migrated from UrbanCanopy.jl@9200edd4 src/hydrology.jl:743 (`WaterTableDepth` @component). Observed-only: z_h_bottom and W_a are parameters and z_v is given by a single algebraic equation.