Supplementary code — Coupled van Genuchten–Mualem parameterization
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Files:
  vgm.py       Unified VGM hydraulic properties (retention, capacity, Mualem Kr,
               alpha* scaling by temperature/salinity/hysteresis, Ks scaling,
               van't Hoff osmotic head).
  richards.py  Mixed-form modified-Picard (Celia et al. 1990) 1D Richards solver
               with advection-dispersion salt transport and reflection-coefficient
               osmotic coupling. Vectorized, Thomas tridiagonal solve.
  run_all.py   Reproduces every numerical value reported in the manuscript.

Run:  python run_all.py     (needs numpy; matplotlib for figures)

All reported numbers are outputs of this code, values from the cited literature,
or statistics from the public UNSODA 2.0 database. No proprietary data are used.
