`<ptfkit/clapp1978.h>`¶

#include <ptfkit/clapp1978.h>

Clapp and Hornberger (1978) representative soil hydraulic parameters by texture.

Source¶

Clapp, R. B., & Hornberger, G. M. (1978). Empirical equations for some soil hydraulic properties. Water Resources Research.

Scope¶

Territory: United States

Dataset: Desorption data reported by Holtan et al. (1968) for soils collected at 34 United States localities; 1,446 soils remained from an initial set of more than 1,800 after the exclusions described by the paper.

PTF catalog page

`clapp1978_usda_texture_class`¶

typedef enum {
    clapp1978_usda_texture_class_sand,
    clapp1978_usda_texture_class_loamy_sand,
    clapp1978_usda_texture_class_sandy_loam,
    clapp1978_usda_texture_class_silt_loam,
    clapp1978_usda_texture_class_loam,
    clapp1978_usda_texture_class_sandy_clay_loam,
    clapp1978_usda_texture_class_silty_clay_loam,
    clapp1978_usda_texture_class_clay_loam,
    clapp1978_usda_texture_class_sandy_clay,
    clapp1978_usda_texture_class_silty_clay,
    clapp1978_usda_texture_class_clay,
} clapp1978_usda_texture_class;

Member	Canonical value	Description
`clapp1978_usda_texture_class_sand`	`sand`	USDA sand soil textural class.
`clapp1978_usda_texture_class_loamy_sand`	`loamy sand`	USDA loamy sand soil textural class.
`clapp1978_usda_texture_class_sandy_loam`	`sandy loam`	USDA sandy loam soil textural class.
`clapp1978_usda_texture_class_silt_loam`	`silt loam`	USDA silt loam soil textural class.
`clapp1978_usda_texture_class_loam`	`loam`	USDA loam soil textural class.
`clapp1978_usda_texture_class_sandy_clay_loam`	`sandy clay loam`	USDA sandy clay loam soil textural class.
`clapp1978_usda_texture_class_silty_clay_loam`	`silty clay loam`	USDA silty clay loam soil textural class.
`clapp1978_usda_texture_class_clay_loam`	`clay loam`	USDA clay loam soil textural class.
`clapp1978_usda_texture_class_sandy_clay`	`sandy clay`	USDA sandy clay soil textural class.
`clapp1978_usda_texture_class_silty_clay`	`silty clay`	USDA silty clay soil textural class.
`clapp1978_usda_texture_class_clay`	`clay`	USDA clay soil textural class.

`clapp1978_parameters`¶

typedef struct {
    double b;
    double saturation_suction;
    double wetting_front_suction;
    double saturated_water_content;
    double saturated_hydraulic_conductivity;
    double sorptivity;
 } clapp1978_parameters;

Field	Description
`b`	Mean exponent of the moisture-characteristic power curve. (1)
`saturation_suction`	Representative saturation suction, calculated as the antilog of the mean logarithm of fitted saturation-suction values. (cm)
`wetting_front_suction`	Representative Green-Ampt wetting-front suction. (cm)
`saturated_water_content`	Mean saturated volumetric water content, taken as total porosity. (1)
`saturated_hydraulic_conductivity`	Mean saturated hydraulic conductivity reported by Li et al. (1976). (cm/min)
`sorptivity`	Representative sorptivity for the paper's single initial moisture deficit corresponding to 500-cm initial suction. (cm/min^(1/2))

Functions¶

`calc_ptf_clapp1978`¶

Return representative soil hydraulic parameters for a USDA texture class.

static inline clapp1978_parameters calc_ptf_clapp1978(clapp1978_usda_texture_class soil_texture);

Parameters¶

Name	Direction	Description
`soil_texture`	in	USDA soil textural class used to select a row of Table 2.

Returns¶

A clapp1978_parameters value.

Note

The representative wetting-front suctions use an inflection wetness of 0.92 to model gradual air entry near saturation.

Note

The sorptivity values use the average saturated hydraulic conductivities reported by Li et al. (1976) and one initial moisture deficit at 500-cm suction.

Warning

The paper states that these unverified average values should not be used blindly because saturation suction varies substantially within texture classes.

Warning

Sorptivity values must be treated cautiously because the conductivity averages may not represent the same average soils as the other parameters.

<ptfkit/clapp1978.h>¶