Version: 1.0 (1985)

Order No: FOS 01

Price: Contact igwmc@mines.edu for more info

FP is a computer program for determining retention function parameters from experimental data. It is a historic model based an early formulation of the general retention function, relating the saturation to the capillary pressure in distributed soils. This function describes the imbibition as well as four readily assessed parameters that either have physical significance themselves, or may be used to determine certain hydraulic properties of the soil. With the assumption that the Burdine integrals are adequate, a relative permeability function has been derived through the substitution of the retention function for the integrands in the Burdine integrals. The permeability function is expressed in terms of the incomplete Beta function ratio whose value may be conveniently found in some mathematical tables. Further, a general pore-sized distribution function of soils has been obtained from the retention function. The derivation of the pore-size distribution function enables more rigorous examination and further exploration of the theories concerning water movement in partially saturated soils.

The program runs in batch mode. It requires an input file which can be prepared with a text editor. Output is a text file with tabular results. FP is a public domain, DOS-based program distributed complete with source code, executable image, and an example data set. The documentation consists of installation instructions, a description of the theory and computer code, and an example application.

**SYSTEM REQUIREMENTS**

Intel 80i86 based computer, 640 Kb RAM, DOS 3.1 or higher, math coprocessor, CGA (no graphics). Note: for a more recent and extended soil parameter estimation code, see RETC.

*Developers: C. Su and R.H. Brooks (Oregon State University)*