Similarities of WEPP with other Models that might be used for Erosion Computations

This is Appendix 8 of the WEPP User Requirements
I. USLE (Universal Soil Loss Equation)
A. Principal application
1. Compute soil loss in conservation planning and inventories
2. Compute soil loss to use to estimate yield for offsite sedimentation and water quality evaluations
B. Major similarities
1. Computes sheet - rill erosion from rainfall
2. Computes average annual soil loss from eroding portions of the landscape
3. Planning and assessment tool for use by field, state, and national office agency personnel
4. Similar inputs
C. Major differences
1. Model structure
a. USLE empirical and lumped
b. WEPP process based
c. WEPP computes by storm
2. Additional computational features of WEPP
a. Deposition in furrows, on concave slopes, at edges of a landuse change, and in concentrated flow channels
b. Concentrated flow erosion
c. Grid version of WEPP allows computations over a field
II. CREAMS (A field scale model for Chemicals, Runoff, and Erosion from Agricultural Management Systems)
A. Principal application
1. Water quality analyses for field sized areas
B. Major similarities
1. Model structure similar but CREAMS more detailed
2. Provide similar hydrologic and erosion estimates
3. Both operate on individual storms
4. WEPP profile and watershed versions and CREAMS model field representations are the same
C. Major differences
1. User environment
a. CREAMS is not intended for day-to-day field operations
2. WEPP does not compute chemical movement
3. CREAMS algorithms are more detailed and thus more powerful
4. CREAMS uses older technology including SCS curve number runoff prediction method and USLE factors (Note: CREAMS is structured so that components can be and are being changed)
5. CREAMS is primarily intended to operate as a continuous simulation model
6. CREAMS is limited to a single crop in a "field"
7. CREAMS has no comparable "grid" model
III. EPIC (Erosion/Productivity Impact Calculator)
A. Principal applications
1. Calculate the loss of crop yield from erosion
B. Major similarities
1. Model components are similar but EPIC much more detailed except for erosion component
2. Operate on individual storms
C. Major differences
1. Thrusts of models
a. EPIC emphasizes the impact of erosion on change in soil and its impact on productivity
b. Main thrust of WEPP is in its erosion estimates as affected in detail by climate, soil, topography and land use
2. EPIC is not intended for day-to-day field operations
3. EPIC is a continuous simulation model
4. EPIC requires more detailed inputs
5. EPIC applies to a point on the landscape and thus does not consider sediment transport, deposition or concentrated flow erosion
IV. SWRRB (Simulator for Water Resources in Rural Basins)
A. Principal applications
1. Efficient computation of sediment yield from small to large, complex watersheds
B. Major similarities
1. Model structure of both estimate sediment yield when SWRRB is applied to WEPP sized areas
2. Both operate on individual storms
3. Both require similar inputs
C. Major differences
1. Model thrusts
a. SWRRB mainly is to deal with sediment yield from large, complex watersheds
b. WEPP deals in detail with erosion and deposition within a field
2. Erosion relationships in WEPP are more process based: SWRRB hydrology and erosion relationships are from the SCS curve number method and the USLE
3. WEPP has very limited routing capability
4. WEPP is aimed to a field user
V. SPUR (Simulation of Production and Utilization of Rangelands)
A. Principal application
1. Evaluation of impact of alternative range management practices
B. Major similarities
1. Model Structure
2. Both estimate sediment yield
3. Both operate on single storms
C. Major differences
1. Model thrusts
a. SPUR has an elaborate plant growth model that considers species interaction and response to environment but is limited to rangeland
b. SPUR has an animal and economics component
c. SPUR is more elaborate and has a complex watershed version
2. Erosion relationships in WEPP are more process based
3. WEPP is aimed to a field user
VI. ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation)
A. Principal application
1. Watershed planning for erosion and sediment yield control on complex watersheds
2. Water quality analysis associated with sediment associated chemicals
B. Major similarities
1. Process based
2. Event based
3. Grid topography representation
C. Major differences
1. ANSWERS is primarily limited to single storm
2. ANSWERS has limited capability for concentrated flow erosion
3. ANSWERS is a fully dynamic model
VII. AGNPS - field scale version (Agricultural Nonpoint Source Pollution Model)
A. Principal application
1. Analysis of nonpoint source pollution from agricultural fields
B. Major similarities
1. Grid based topographic representation
2. Process and hydrologically driven
3. Considers multiple particle classes
C. Major differences
1. AGNPS relies on older hydrologic and erosion prediction technology
2. AGNPS has limited capabilities for estimating concentrated flow erosion
VIII. SEDIMOT II (SEdimentology by DIstributed MOdel Treatment)
A. Principal application
1. Design of sediment control structure on surface mined land
B. Major similarities
1. Process and hydrologically driven
2. Considers multiple particle classes
C. Major differences
1. Single event model
2. One option uses older hydrologic (SCS curve number) and erosion (USLE) prediction technology
3. Provide a more detailed analysis of impoundments and other such sediment control structures

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