Oleson-2010

Net water-input rate for the pervious-road column (Oleson et al. 2010, CLM Tech Note Ch. 5, Eq. 5.1, p. 110). Migrated from UrbanCanopy.jl@9200edd4 src/hydrology.jl:900 (`PerviousRoadWaterBalance` @component). Algebraic single-equation balance: water_input = (precipitation gains) − (evaporation + surface runoff + sub-surface drainage + groundwater liquid runoff + snow-capping solid runoff).

Combined-layer properties when two snow layers are merged (Oleson et al. 2010, Section 5.1.5.1, Eqs. 5.38–5.42). Migrated from UrbanCanopy.jl@9200edd4 src/hydrology.jl:253 (`SnowLayerCombination` @component). Observed-only: per-layer thicknesses, water/ice contents, and temperatures are inputs (parameters); combined thickness/water/ice/enthalpies/temperature are algebraic outputs.