1. General Model Information



Main medium: terrestrial
Main subject: biogeochemistry
Organization level: ecosystem
Type of model: ordinary differential equations, not specified
Main application: decision support/expert system, simulation/optimisation tool
Keywords: grasslands, water-balance, yield indices, ET


J. Ross Wight
800 Park Blvd. Suite 105 Boise, ID 83712
Phone: 208-334-1363
Fax : 208-334-1502
email: rwight@nwrc.ars.pn.usbr.gov


Wight, J.R., K.A. Gebhardt, A.L. Huber, and C.L. Hanson.


The RANGETEK model is a modified version of the ERHYM -II model. It includes expert system technology to improve the ease of data input and interpretation of output data. The model provides simulation of daily water-balance and calculation of annual yield indices based on the ratio of actual to potential transpiration (Wight et al., 1990).

Validation Procedures: Model outputs of soil water content and evapotranspiration (ET) were compared to field-measured values. Predicted herbiage yields were compared to field-measured herbiage yields.
How Model Functions: The model runs on a daily time step with daily inputs of maximum and minimum air temperatures and solar radiation. Water added to the soil profile is the difference between precipitation and runoff. The SCS curve number procedure as described in CREAMS is used to estimate runoff. As each soil layer is filled to its water holding capacity, water is cascaded down to the next soil layer. When the profile is full, surplus water becomes drainage. Potential ET is calculated by a modified Penman equation as described in SPUR. Actual soil and plant evaporation are based on potential ET, soil water content, average site LAI and a relative growth curve. A soil temperature routine from EPIC and a solar radiation generating routine is included

Author of the abstract:


II. Technical Information

II.1 Executables:

Operating System(s): 640 K of memory, a color monitor, and DOS 3.0 or better operatingsystem.

II.2 Source-code:

Programming Language(s): BASIC and C++.

II.3 Manuals:

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

Daily precipitation, maximum and minimum air temperaturesand solar radiation; field capacity and permanent wilting water contents for each soil layer; initialsoil water content; average site herbiage yield at peak standing crop; and dates for start ofgrowing season, peak standing crop, and end of growing season. Calculated daily values of potential and actual soil and plant evaporation

III.2.2 Output

Calculated daily values of potential and actual soil and plant evaporationfrom each soil layer, daily soil water contents, cumulative actual and potential transpiration, andgraphic display of these values.

Temporal Scale: Daily time step

Spatial Scale: Range site specific

IV. References

Wight, J.R., K.A. Gebhardt, A.L. Huber, and C.L. Hanson. 1990. RANGETEK; adecision aid for range management, p. 179-185. E.B. James and W.R. Hotchkiss(eds.), Transferring Models to Users, Symp. Proc. Denver, CO, Nov. 4-8. Amer.Water Resources Assoc. Bethesda, MD.

V. Further information in the World-Wide-Web

VI. Additional remarks

The ERHYM - II model could be used to quantify the impacts of managementactivities, conservation measures, and projected global changes on westernUnited States grasslands.

Last review of this document by: T. Gabele: 08. 07. 1997 -
Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:48 CEST 2002

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