# Water content

DIN ISO 11465
Area Soil condition
title Determination of dry residue and water content based on mass - gravimetric method (ISO 11465: 1993)
Latest edition 1996-12
ISO 11465

The water content indicates the amount of water that is contained in a material. In addition to the volumetric water content , which relates to the volume fraction of the water in the sample, there is also the gravimetric water content , which relates to the mass fraction . The definition of the water content is given in ISO 11465.

Typical materials for which the water content is relevant are, for example, soil and food .

## Volumetric and gravimetric water content

The volumetric water content indicates the water volume in relation to the total volume ( volume fraction , outdated "volume percent"): ${\ displaystyle \ theta}$${\ displaystyle V_ {w}}$${\ displaystyle V_ {T}}$

${\ displaystyle \ theta = {\ frac {V_ {w}} {V_ {T}}}}$

The gravimetric water content relates the water mass , i.e. the difference between wet mass and dry mass, to the dry mass of the material. Values ​​over 100% are possible for the water content: ${\ displaystyle w}$${\ displaystyle m_ {w}}$${\ displaystyle m_ {f}}$${\ displaystyle m_ {d}}$

${\ displaystyle w = {\ frac {m_ {w}} {m_ {d}}} = {\ frac {m_ {f} -m_ {d}} {m_ {d}}}}$

For biomass , e.g. B. wood , the gravimetric water content is normally related to the wet mass and thus corresponds to the mass fraction :

${\ displaystyle w = {\ frac {m_ {w}} {m_ {d} + m_ {w}}} = {\ frac {m_ {f} -m_ {d}} {m_ {f}}}}$

The different definitions of the water content can be converted into one another with known densities .

## Measurement method

Various methods are available to determine the water content of a soil. In addition to oven drying or the radiometric method, it is possible to determine the water content with the flame method . With this field method, the soil sample is dried with a so-called flame liquid (for example denatured alcohol ). The standardization by the corresponding set of rules was withdrawn in 2007.

In medical imaging examinations such as ultrasound or computed tomography , the level of water content is often recognizable from the brightness of an image point or voxel , which also provides information on the condition of soft body tissue.

## Norms and standards

• DIN ISO 11465: 1996-12 Soil quality - Determination of dry residue and water content on the basis of mass - Gravimetric method
• DIN ISO 11461: 2002-05 Soil quality - Determination of the water content of the soil as a volume fraction using a sample cylinder - Gravimetric method
• DIN EN 14774-1: 2010-02 Solid biofuels - Determination of water content - Oven drying - Part 1: Total water content - Reference method
• Technical test regulations for soil and rock in road construction (TP BF-StB)