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Soil Series Horizon Properties

HORIZON Hydraulics

Soil Series Horizon Hydraulic Data

HORIZON Hydraulics is tabular data that can be used in conjunction with any of the NATMAP products, excepting NATMAP soilscapes.

HORIZON Hydraulics includes very detailed descriptions of the hydraulic properties pertaining to each layer, or horizon for each of the soils. This data is based heavily on laboratory based analyses.

Version 2.0 released in November 2014 corrects some anomalies and minimises the larger predictive errors. A new set of predictive equations was derived using an expanded set of measured data from England, Wales, Scotland and Northern Ireland (Hollis et al, 2014). The methodology used to derive the equations has resolved the former problems with respect to poor prediction of water retention in soils with relatively ‘extreme’ mineral particle-size distributions. It has also substantially reduced problems relating to anomalies, between predicted values at increasing pressure heads. Any such remaining anomalies have been eliminated from the dataset. A paper has recently been published which describes the new predictive equations.

Hollis, J. M., Lilly, A., Higgins, A., Jones, R. J. A. Keay, C. A. and Bellamy, P.H. (2014). Predicting the water retention characteristics of UK mineral soils. European Journal of Soil Science, 2014, doi: 10.1111/ejss.12186

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HORIZON Hydraulics data and description

The table below describes the various properties within this data product. Each table contains the information outlined below.

Property Example from data Description
HORID 1 Unique Horizon Identifier (Defines one Horizon (depth range, series, landuse))
SERIES 17 Soil series code for each series, this is a 4 digit numeric code
LU_GROUP PG Landuse Group - AR (Arable) PG (Permanent Grass) LE (Ley Grassland) or OT (Other)
DESIGNATION E Layer Designation - At a basic level A (Topsoil) B (subsoil) C (Parent Material) E (Elluvial) O (Organic)
UPPER_DEPTH 20 Horizon upper depth in cm (<0 indicated litter layer)
LOWER_DEPTH 35 Horizon lower depth in cm (999 implies depth below bottom of profile)
BULK_DENSITY 1.29 Bulk density of fine earth (g/cm3)
PARTICLE_DENSITY 2.63 Calculated particle density (g/cm3)
TOTAL_POROSITY 51.1 Total pore space (%) volume - Shardlow data
THV0 28.7 Water content at saturation (% vol)
THV1 26.6 Empirical water content at -1 kPa tension (% vol)
THV5 18.3 Volumetric water content (%) at 5 kPa tension (field capacity)
THV10 15.8 Volumetric water content (%) at 10 kPa suction (equated with field capacity in sandy soils
THV40 11.2 Volumetric water content (%) at 40 kPa suction
THV200 7.7 Volumetric water content (%) at 200 kPa suction
THV1500 5.1 Volumetric water content (%) at 1500 kPa suction (wilting point)
KSAT_SUBVERT 653.9 Saturated hydraulic conductivity (sub-vertical) cm/day
KSAT_LAT 653.9 Saturated hydraulic conductivity (lateral) cm/day
VG_TH_S 0.3 Van Genuchten's water content at quasi-saturation (w/w)
VG_TH_R 0.0285 Van Genuchten's residual water content (w/w)
VG_ALPHA 0.1326 Van Genuchtens 'alpha' parameter
VG_N 1.5385 Van Genuchtens 'n' parameter
VG_M 0.35 Van Genuchtens 'm' parameter
BC_TH_S 0.387 Brook’s Corey water content at saturation (vol fraction)
BC_ALPHA 37.6581 Brook’s Corey 'alpha' parameter
BC_BETA 3.3264 Brook’s Corey 'beta' parameter

Note: Quality information (*_QA) relevant to the texture, organic carbon and pH values is provided. Where the data is averaged from measured sample data the standard deviation is recorded unless their were too few samples in which case Not Applicable (NA) is entered. In some cases an expert soil scientist provided a meaningful value for the parameter in which case the value is labeled 'EXPERT'. Where no meaningful value is derivable a reason is given whether as a result of rock, rubble, ironpan or peat. The coarse and medium sand values have as yet only been derived for the 'A' horizons, therefore subhorizons are labeled 'ND' for Not Derived.