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WEPP Soil File Parameters

Derived from soil-file.spec.md and wepppy/wepp/soils/utils/wepp_soil_util.py. The heading line is the default usersum <parameter> description; bullets expand on extended context or units.

datver — Soil file version code (real)

  • Context: header
  • Extended: Determines how subsequent records are parsed (e.g., 97.5 base format, 2006.2 restrictive layer, 7777/7778 horizon properties, 9002/9003/9005 disturbed/revegetation formats).

solcom — Soil file comment line (text)

  • Context: header
  • Extended: Free-form line (80 characters) carried into generated output for documentation.

ntemp — Number of OFEs or channels (integer)

  • Context: header
  • Extended: Count of overland flow elements or channels described in the file; governs how many OFE records follow.

ksflag — Internal hydraulic conductivity adjustment flag (integer)

  • Context: header
  • Extended: 0 keeps conductivity fixed; 1 allows WEPP to apply internal adjustments during simulation.

OFE Records (Line 4)

slid — Soil identifier for the OFE (text)

  • Context: OFE base
  • Extended: Name of the soil series/profile applied to the element or channel.

texid — Soil texture description (text)

  • Context: OFE base
  • Extended: Textural class label (e.g., "silt loam") associated with the soil profile.

nsl — Number of soil layers (integer)

  • Context: OFE base
  • Extended: Controls how many horizon records follow for the OFE.

salb — Bare-soil albedo (real)

  • Context: OFE base
  • Extended: Albedo of the dry soil surface used for energy balance calculations.

sat — Initial porosity saturation (m³/m³, real)

  • Context: OFE base
  • Extended: Fraction of total porosity considered filled at the simulation start; defaults to 0.75 if unspecified.

ki — Baseline interrill erodibility (kg·s/m⁴, real)

  • Context: OFE base
  • Extended: Governs raindrop-driven soil detachment for interrill (sheet) areas.

kr — Baseline rill erodibility (s/m, real)

  • Context: OFE base
  • Extended: Governs flow-driven detachment within rills.

shcrit — Baseline critical shear stress (N/m², real)

  • Context: OFE base
  • Extended: Minimum hydraulic shear required to initiate soil detachment in rills.

avke — Surface effective hydraulic conductivity (mm/h, real)

  • Context: OFE base
  • Extended: Only present in version ranges > 94.1 and < 2006.2; represents the effective conductivity of the surface layer.

Disturbed / 9000-Series OFE Extensions

ksatadj — Hydrophobicity / conductivity adjustment flag (integer)

  • Context: OFE 9000-series
  • Extended: 0 disables saturation-based adjustments; 1 triggers WEPP's internal hydrophobicity or burn-severity logic.

luse — Disturbed land-use classification (text)

  • Context: OFE 9000-series
  • Extended: Descriptor of the disturbed class (e.g., "forest high sev"); influences burn severity coding and conductivity adjustments.

stext — Simplified soil texture class (text)

  • Context: OFE 9000-series
  • Extended: One of clay loam, loam, sand loam, or silt loam; paired with texid_enum in 9005.

ksatfac — Lower bound on effective conductivity (mm/h, real)

  • Context: OFE 9002 and earlier formats
  • Extended: Defines the minimum effective hydraulic conductivity used in exponential recovery formulations.

ksatrec — Conductivity recovery coefficient (1/day, real)

  • Context: OFE 9002 and earlier formats
  • Extended: Exponential recovery rate toward pre-disturbance conductivity following hydrophobic events.

burn_code — Encoded burn severity class (integer)

  • Context: OFE 9003/9005
  • Extended: Combines land cover and severity (100 agriculture, 200 shrub, 300 forest, etc.), adding 1/2/3 for low/moderate/high severity.

lkeff — Lower limit on effective conductivity (mm/h, real)

  • Context: OFE 9003/9005
  • Extended: Caps the downward adjustment of effective conductivity; -9999 disables the limit.

texid_enum — Simplified texture enumeration (integer)

  • Context: OFE 9005
  • Extended: Maps stext to 1 = clay loam, 2 = loam, 3 = sand loam, 4 = silt loam.

uksat — Upper limit on effective conductivity (mm/h, real)

  • Context: OFE 9005
  • Extended: WEPPcloud-specific parameter used to bound conductivity during revegetation scenarios; consult future documentation for refinements.

Horizon Records (Layer Data)

solthk — Depth to bottom of layer (mm, real)

  • Context: Horizon all versions
  • Extended: Monotonically increasing depth defining soil layer thickness.

sand — Sand fraction by volume (%)

  • Context: Horizon all versions
  • Extended: Percentage of sand in the layer; combined with clay to estimate silt.

clay — Clay fraction by volume (%)

  • Context: Horizon all versions
  • Extended: Used alongside sand to infer texture and hydrologic properties.

orgmat — Organic matter fraction by volume (%)

  • Context: Horizon all versions
  • Extended: Volume percentage of organic material in the layer.

cec — Cation exchange capacity (meq/100 g, real)

  • Context: Horizon all versions
  • Extended: Influences nutrient exchange and is used in empirical conductivity estimates.

rfg — Rock fragment volume fraction (%)

  • Context: Horizon all versions
  • Extended: Fraction of coarse fragments affecting storage and infiltration.

Additional Properties (≥ 7777)

bd — Bulk density (g/cm³, real)

  • Context: Horizon ≥ 7777
  • Extended: Mass density of the soil layer; defaults to 1.4 g/cm³ if missing during conversions.

ksat — Saturated hydraulic conductivity (mm/h, real)

  • Context: Horizon ≥ 7777
  • Extended: Vertical saturated conductivity used in infiltration computations.

fc — Field capacity (m³/m³, real)

  • Context: Horizon ≥ 7777
  • Extended: Volumetric water content at field capacity; estimated via Rosetta when absent.

wp — Wilting point (m³/m³, real)

  • Context: Horizon ≥ 7777
  • Extended: Volumetric water content at permanent wilting; estimated via Rosetta when absent.

Additional Properties (≥ 7778)

anisotropy — Conductivity anisotropy ratio (real)

  • Context: Horizon ≥ 7778
  • Extended: Ratio of horizontal to vertical saturated conductivity; defaults to 10 for very shallow layers when derived.

Rosetta-Derived Parameters (9002+ Horizons)

theta_r — Residual volumetric water content (m³/m³, real)

  • Context: Horizon ≥ 9002
  • Extended: Pedotransfer estimate from Rosetta appended after the primary horizon fields.

theta_s — Saturated volumetric water content (m³/m³, real)

  • Context: Horizon ≥ 9002
  • Extended: Rosetta-derived value representing saturated storage.

alpha — van Genuchten alpha parameter (1/cm, real)

  • Context: Horizon ≥ 9002
  • Extended: Controls capillary pressure head response in the van Genuchten model.

npar — van Genuchten pore-size exponent (dimensionless)

  • Context: Horizon ≥ 9002
  • Extended: Governs the slope of the soil water retention curve.

ks — Rosetta saturated hydraulic conductivity (cm/day, real)

  • Context: Horizon ≥ 9002
  • Extended: Pedotransfer prediction (different units from ksat); WEPP may convert internally for hydraulic calculations.

wp_ros — Rosetta-derived wilting point (m³/m³, real)

  • Context: Horizon ≥ 9002
  • Extended: Appended after the base horizon record; WEPP retains both measured and pedotransfer estimates.

fc_ros — Rosetta-derived field capacity (m³/m³, real)

  • Context: Horizon ≥ 9002
  • Extended: Pedotransfer estimate appended alongside theta_r/theta_s.

Restrictive Layer (Line 6)

slflag — Restrictive layer presence flag (integer)

  • Context: Restrictive layer
  • Extended: 0 indicates no restricting layer; 1 activates the restricting-layer parameters.

ui_bdrkth — Restrictive layer thickness or depth (mm, real)

  • Context: Restrictive layer
  • Extended: Depth to bedrock or restricting layer where runoff/percolation properties change.

kslast — Restrictive layer hydraulic conductivity (mm/h, real)

  • Context: Restrictive layer
  • Extended: Saturated conductivity assigned to the bottom layer or bedrock interface; often derived from the last horizon (ksat/100).