Soil Erosion Network: Model Metadata
ACRU Agrohydrological Modelling System

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1. Model identification Soil Erosion Network - Model
1.1 Model name
1.2 Most recent version ACRU 3.0
1.3   Date of release February 1995.
2. Water erosion
3. Contact person
3.1 Name Simon A Lorentz
3.2 Address Dept Agricultural Engineering, University of Natal, Box X01, Scottsville, South Africa
3.3 Tel +27 331 2605701
3.4 Fax +27 331 2605818
3.5 Email
4. Model Author(s) Professor Roland Schulze, Hydrology
Dr Simon Lorentz (et al) Sediment Yield.
5. Model components
5.1   Water erosion: Modified universal soil loss equation with RUSLE parameters. K factor moisture content dependant. GIS based evaluation of parameters.
5.2 Wind erosion: None
5.3 Hydrology: . Daily soil water budget. SCS with updated soil water redistribution
5.4 Site/topography: Latitude and longitude. Slope
5.5 Plant growth: Maize model.
5.6 Management: Simulates surface roughness
5.7 Soil: Mode 1 A and B horizon
Mode 2 20 user defined layers
5.8 Chemistry: P and E-Coli considered.
5.9 Weather: Daily weather data
6. Model characteristics
6.1 Spatial
6.1.1 Class of area: Catchment: Mode 1.
Point or Field: Mode 2
6.1.2  Flow routing system: Muskingum routing between sub-catchments
6.1.3 Minimum area: Point.
6.1.4 Maximum area: Not advised for > 50 km2
6.2. Temporal
6.2.1 Timestep: . Mode 1: Daily.
Mode 2: Break point or 1 minute.
6.2.2 Single or multiple event? Multiple
6.2.3 Maximum simulation duration: System limitation is 150 years (daily)
7 Model's representation of processes
7.1 Water erosion processes
7.1.1 Interrill: Lumped with rill using. RUSLE
7.1.2 Rill: Lumped
7.1.3 Gully: Not modelled separately. Subject of current study
7.1.4 Streambank: -
7.1.5 Deposition: Only in terms of RUSLE LS factor
7.2 Wind erosion processes:
7.2.1 Creep/surface roll: None
7.2.2 Saltation:
7.2.3 Suspension:
7.3 Hydrological processes:
7.3.1 Evaporation/transpiration: Selection of: Expert system. A - pan, Penman, Margreaves, Limacre, Blaney-Criddle, Thoruthwaite
7.3.2 Runoff: Mode 1. Daily water budget.
SCS with updated soil water content and redistribution.
Mode 2. Excess from Green - Ampt.
7.3.3 Infiltration: Mode 1. Difference between effective rain and runoff. Unsaturated redistribution
Mode 2. Green - Ampt and Richards equ. redistribution.
7.3.4 Subsurface flow: Mode 1. Cascading layers with user define response parameters.
Mode 2. Richards equ with constant head boundary.
7.3.5 Return flow: Mode 1. User defined response rate
7.4 Plant processes:
7.4.1 Light interception and photosynthesis: Through crop coefficient. Leaf area index and degree day
7.4.2 Dry matter and residue: Specified in RUSLE C factor.
7.4.3 Root growth: Specified in RUSLE C factor. Growth in irrigation routine.
7.4.4 Pests: None
7.4.5 CO2 sensitivity: Through sensitivity of transpiration suppression. Select C3 or C4 plant.
7.5 Soil: Mode 1. A and B horizon + baseflow response - cascading layers.
Mode 2. 20 layers retention + hydraulic characteristics green - ampt and Richards equ
7.5.1 Crust development: Mode 2: Exponential equ.
7.5.2 Aggregate properties: Used in specification option for defining hydraulic properties. Used in specifying RUSLE K factor in sediment yield.
7.6 Chemistry:
7.6.1 Nutrients: In irrigation option. Nitrate and phosphorus in water quality option.
7.6.2 Carbon: None
7.6.3 Pesticides: None
7.6.4 Other contaminants: Phosphorus and e-coli
7.7 Weather: On-line real time mode is planned
8. Input Data (* = Mandatory)
8.1 Weather: Daily precipitation*, Max*, Min* temperature, Relative humidity, wind speed, a pan data, radiation.
8.2 Soil: Physical characteristics* of each layer - Texture, porosity, WP, FC - or soil form and series* mandatory or A-B horizon response, B-T horizon response - HC for each layer. Surface K* factor for sediment yield.
8.3 Hydrology Coefficient of baseflow response*. Coefficient of quickflow response*. Impervious area*. Coefficient of initial abstraction*. Critical depth of soil from which stormflow takes place*
8.4 Plant cover: Crop coefficient* - Leaf area index*. C factor for sediment yield. Interception loss* - Fraction of root in topsoil*, effective root depth* orcrop/type vegetation.
8.5 Soil surface cover: Depth of A & B horizons. Cracking soil (clay content class).
8.6 Management: P factor for sediment yield. Mode 2: Soil roughness
8.7 Topography/site characteristics: Time of concentration (*for sediment yield). Slope (for peak flow). Hydraulic length - altitude, lat, long catchment area*
8.8 Micro-topography: Mode 2: Soil roughness - decrease of roughness with rainfall after tillage.
9. Output data: Daily, monthly or annual values of any variable calculated in the program. Specified in output option program. Typically: rainfall, effective rain, evap (pot & actual) soil water content, quickflow, total runoff, peakflow, sediment yield.
10    Programming Language: PC : Fortran or Unix : Fortran 77
11 Computer requirement: PC : 560KB RAM 20 mb disk space. Storage of output (daily) 98kb per subcatchment (all variables) per year. 16kb/sc/ (10 variables per year. Unix enquire CCWR.
12    Documentation
12.1 Scientific Documentation Hydrology and Agrohydrology: A text to accompany the ACRU 3.00 Agrohydrological Modelling System. Schulze, R. 1995. WRC report II
12.2 User's guide ACRU - Agrohydrological Modelling System. User Manual v3.00. Smithers, J. and Schulze, R. 1995. Water Research Commission (WRC) Report II 70/95, Pretoria, South Africa.
12.3 Technical Documentation None
13 Availability On Request
14 Other Relevant Information Future planning. GIS-model direct link. Real time modelling. Enhancement of soil water & sediment yield processes.

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