Depth to water and depth to a potentiometric surface

Depth equals land-surface elevation minus head after explicit geometry, unit, and datum checks. Negative values are retained for review rather than clipped. They can reflect artesian conditions, discharge, local interpolation behavior, measurement or DEM uncertainty, or incompatible references. A confined potentiometric surface is not relabeled a water table.

depth <- ps_depth_to_water_surface(head, dem, surface_type="potentiometric")