| 1
Model identification |
Soil
Erosion Network - Model |
|
|
|
1.1
Model name |
EPIC
- Water and Wind Erosion |
|
1.2
Most recent version |
EPIC
8120
(updated
12/2000) |
|
1.3
Date of release |
August
1994 |
|
|
| 2
Water erosion and Wind Erosion |
|
|
|
| 3
Contact person |
|
|
3.1
Name |
J.
R Williams |
|
3.2
Address |
USDA-ARS,
808 E Blackland Road,
Temple,
TX 76503
USA |
|
3.3
Tel |
+1
817 770 6508 |
|
3.4
Fax |
+1
817 770 6561 |
|
3.5
Email |
williams@brcsun0.tamu.edu |
|
| 4
Model Author(s) |
J
Williams, J Arnold, J Kiniry, K Potter, K King |
|
| 5
Model components |
|
5.1
Water erosion: |
USLE/MUSLE
(several variations) |
|
5.2
Wind erosion: |
Modified
Manhattan KS model (Bagnold energy component) |
|
5.3
Hydrology: |
Runoff-
modified SCS CN; Peak rate-modified rational or SCS TR-55; ET=
4 options, Penman, Penman-Montieth, Hargreaves, Priestly-Taylor |
|
5.4
Site/topography: |
Whole
Farm/small watershed/landscape; watershed may be subdivided |
|
5.5
Plant growth: |
General
crop growth model simulates about 30 crops |
|
5.6
Management: |
Irrigation,
fertilizer, liming, furrow diking, crop rotation. Variety of
tillage operations |
|
5.7
Soil: |
Up
to 30 soil layers. Core data - Bulk density, field capacity,
wilting point, organic CO texture |
|
5.8
Chemistry: |
N
and P cycling; pesticide fate; water quality |
|
5.9
Weather: |
Precipitation,
temperature (max, min) solar radiation, relative humidity, wind
(speed & direction). Input or generated |
|
| 6
Model characteristics |
|
6.1
Spatial |
|
|
|
6.1.1
Class of area: |
Whole
farm, small watershed, landscape |
|
|
6.1.2
Flow routing system: |
Streamline
- natural subareas |
|
|
6.1.3
Minimum area: |
1
ha |
|
|
6.1.4
Maximum area: |
100
km2 |
|
6.2.
Temporal |
|
|
|
6.2.1
Timestep: |
1
day |
|
|
6.2.2
Single or multiple event? |
Continuous |
|
|
6.2.3
Maximum simulation duration: |
1000
years |
|
|
| 7
Model's representation of processes |
|
|
7.1
Water erosion processes |
|
|
|
7.1.1
Interrill: |
Combined |
|
|
7.1.2
Rill: |
Combined |
|
|
7.1.3
Gully: |
None
now - development is high priority |
|
|
7.1.4
Streambank: |
Yes
- sediment routing degrades channel as a function of flow velocity |
|
|
7.1.5
Deposition: |
Yes
- governed by flow velocity and particle size |
|
7.2
Wind erosion processes: |
|
|
|
7.2.1
Creep/surface roll: |
Yes
- Bagnolds eg |
|
|
7.2.2
Saltation: |
Yes
- Bagnolds eg |
|
|
7.2.3
Suspension |
Yes
- Bagnolds eg |
|
|
|
|
7.3
Hydrological processes: |
|
|
|
7.3.1
Evaporation/transpiration: |
Penman,
Penman - Montieth, Hargreaves, Priestly- Taylor |
|
|
7.3.2
Runoff: |
SCS
CN modified for volume; modified rational of SCS TR55 for peak
rate |
|
|
7.3.3
Infiltration |
SCS
CN modified |
|
|
7.3.4
Subsurface flow: |
Yes
- lateral and vertical computed simultaneously when field capacity
is exceeded. Vertical governed by saturated conductivity; lateral
by land slope |
|
|
7.3.5
Return flow |
Yes
- function of lateral flow and subsurface travel time from watershed
centroid to outlet |
|
|
|
|
7.4
Plant processes: |
|
|
|
7.4.1
Light interception and photsynthesis: |
Yes
- Beer's law; potential daily biomass growth limited by minimum
stress factor - water, nutrients, temperature, aeration |
|
|
7.4.2
Dry matter and residue |
Yes
- at harvest yield is removed (harvest index). Standing dead
residue falls to the soil surface at a rate driven by accumulated
rainfall, and surface & subsurface residue is decayed as
a function of soil moisture and temperature |
|
|
7.4.3
Root growth: |
Depth
driven by heat units ; limited to max for crop or soil depth.
Root mass a function of water use. Limited by bulk density,
aluminium saturation, or temperature |
|
|
7.4.4
Pests: |
Insects,
weeds, diseases. Generic model driven by moisture, temperature
& biomass |
|
|
7.4.5
CO2 sensitivity: |
Through
canopy resistance in Penman-Montieth equation and crop coefficient
converting energy to biomass |
|
|
|
|
7.5
Soil: |
Up
to 30 layers permitted with variable thickness. Erosion removes
soil from profile; layer 2 becomes thinner until it approaches
O, then removed from system. Properties change with erosion,
tillage mixing, mineralization of organic matter |
|
|
7.5.1
Crust development |
Not
modelled |
|
|
7.5.2
Aggregate properties |
- |
|
|
|
|
7.6
Chemistry: |
|
|
|
7.6.1
Nutrients: |
N
& P cycles - mineral, organic (NO3, NH3,
active & stable organic N; labile P, active and stable mineral
and organic P. Water and sediment transport, crop uptake, mineralization-
immobilization nitrification, denitrification, N fixation, volatilization |
|
|
7.6.2
Carbon |
Tracks
organic N |
|
|
7.6.3
Pesticides |
GLEAMS
pesticide component. Wash off of plants, decay in soil &
on foliage, leaching, runoff and sediment transport |
|
|
7.6.4
Other contaminants |
None |
|
|
|
|
7.7
Weather: |
Precipitation,
temperature (max & min), solar radiation, wind speed, relative
humidity. Input or generated |
|
| 8
Input Data (* = Mandatory) |
|
8.1
Weather: |
Required:
Precipitation, temperature (monthly means) optional; solar radiation,
wind speed, relative humidity |
|
8.2
Soil: |
Required:
Bulk density, texture, Organic C, optional field capacity, wilting
point, saturated conductivity, % rock, pH, sum of bases, CEG,
AL saturation, CACO3, labile P, mineral P active
& stable, NO3, Organic N active & stable |
|
8.3
Hydrology: |
SCS
CNa, watershed area, channel length & steepness,
Mannings N, Optional: channel depth |
|
8.4
Plant cover: |
Crop
parameter table; planting and harvest dates |
|
8.5
Soil surface cover: |
Initial
standing & flat residue |
|
8.6
Management: |
Tillage
table; operation schedule (complete crop rotation by dates) |
|
8.7
Topography/site characteristics: = |
Land
slope & steepness, Mannings N |
|
8.8
Micro-topography: |
Random
roughness and ridge interval & height created by each tillage
operation |
|
| 9
Output data |
Weather,
hydrology, erosion, nutrients, pesticides, crop production,
soil properties. By sub-area, routing reach, and total watershed.
Option S-daily, monthly, annual; user selects outputs |
|
| 10
Programming language |
Fortran |
|
| 11
Computer requirements |
IBM
PC compatible with at least 640K |
|
| 12
Documentation |
|
12.1
Scientific documentation: |
Sharpley
& Williams, 1990. EPIC-Erosion/Productivity Impact Calculator:
1. Model Documentation, USDA Tech Bull # 1768.12.2 |
|
12.2
User's guide: |
EPIC
User's Guide; USDA ARS SCS, and TAES; Vanicek & Dameshil
Editors |
|
12.3
Technical documentation: |
Sharpley
& Williams, 1990. EPIC-Erosion/Productivity Impact Calculator:
2. User Manual. |
|
| 13
Availability |
Upon
request from developer |
| 14
Other Relevant Information |
- |
|
