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<ptfkit/rawls1982.h>

#include <ptfkit/rawls1982.h>

Rawls et al. (1982), water-retention regressions for soils across the USA.

Source

Rawls, W. J., Brakensiek, D. L., & Saxton, K. E. (1982). Estimation of soil water properties. Transactions of the ASAE, 25, 1316-1320.

Scope

Territory: Agricultural soils from 32 states of the USA

Dataset: 1,323 soils with about 5,350 horizons; regression equations used 2,541 horizons.

PTF catalog page

rawls1982_ptf_result

typedef struct {
    double theta_4;
    double theta_7;
    double theta_10;
    double theta_20;
    double theta_33;
    double theta_60;
    double theta_100;
    double theta_200;
    double theta_400;
    double theta_700;
    double theta_1000;
    double theta_1500;
 } rawls1982_ptf_result;
Field Description
theta_4 Volumetric water content at -4 kPa. (cm^3/cm^3)
theta_7 Volumetric water content at -7 kPa. (cm^3/cm^3)
theta_10 Volumetric water content at -10 kPa. (cm^3/cm^3)
theta_20 Volumetric water content at -20 kPa. (cm^3/cm^3)
theta_33 Input volumetric water content at -33 kPa. (cm^3/cm^3)
theta_60 Volumetric water content at -60 kPa. (cm^3/cm^3)
theta_100 Volumetric water content at -100 kPa. (cm^3/cm^3)
theta_200 Volumetric water content at -200 kPa. (cm^3/cm^3)
theta_400 Volumetric water content at -400 kPa. (cm^3/cm^3)
theta_700 Volumetric water content at -700 kPa. (cm^3/cm^3)
theta_1000 Volumetric water content at -1000 kPa. (cm^3/cm^3)
theta_1500 Input volumetric water content at -1500 kPa. (cm^3/cm^3)

Functions

calc_ptf_rawls1982_theta_1500

Estimate volumetric water content at -1500 kPa.

static inline double calc_ptf_rawls1982_theta_1500(double clay, double organic_matter);

Parameters

Name Direction Description
clay in Clay content. (%)
organic_matter in Organic matter content. (%)

Returns

Volumetric soil water content at -1500 kPa. (cm^3/cm^3)

calc_ptf_rawls1982_theta_33

Estimate volumetric water content at -33 kPa using measured or estimated theta_1500.

static inline double calc_ptf_rawls1982_theta_33(double sand, double organic_matter, double theta_1500);

Parameters

Name Direction Description
sand in Sand content. (%)
organic_matter in Organic matter content. (%)
theta_1500 in Measured or estimated volumetric water content at -1500 kPa. (cm^3/cm^3)

Returns

Volumetric soil water content at -33 kPa. (cm^3/cm^3)

calc_ptf_rawls1982_full_wrc

Estimate a twelve-point water-retention curve using theta_33 and theta_1500.

static inline rawls1982_ptf_result calc_ptf_rawls1982_full_wrc(double sand, double organic_matter, double bulk_density, double theta_33, double theta_1500);

Parameters

Name Direction Description
sand in Sand content. (%)
organic_matter in Organic matter content. (%)
bulk_density in Bulk density. (g/cm^3)
theta_33 in Measured or estimated volumetric water content at -33 kPa. (cm^3/cm^3)
theta_1500 in Measured or estimated volumetric water content at -1500 kPa. (cm^3/cm^3)

Returns

A rawls1982_ptf_result value.

Note

The source offers three regression levels; this function uses measured theta_33 and theta_1500 for the intermediate points.

Warning

The source value 0.8888 is retained literally for the theta_7 intercept.