Overview
EN ISO 11275:2014 (identical to ISO 11275:2004) specifies a laboratory procedure - Wind's evaporation method - for the simultaneous determination of unsaturated hydraulic conductivity and the soil water‑retention characteristic. The method measures the drying (desorption) curve of homogeneous, preferably undisturbed soil samples by combining tensiometer readings with periodic mass measurements as the sample dries by evaporation from the top surface.
Key constraints:
- Applicable only to the drying/desorption branch of the water‑retention curve.
- Not suitable for soils that shrink within matric head range 0 cm to −800 cm.
- Conductivity determination range ≈ −50 cm to −700 cm matric head.
- Water‑retention determination range ≈ 0 cm to −800 cm matric head.
Key Topics
- Principle: Samples are wetted near saturation, allowed to dry by evaporation, and monitored until air enters any tensiometer. Tensiometers record matric (pressure) head at multiple depths while sample mass is logged to compute volumetric water content.
- Sample requirements: Preferably homogeneous, undisturbed samples taken per sampling guidance (e.g., ISO 10381‑1).
- Measurement parameters: Tensiometer pressure heads, compartmental water contents (sample subdivided by tensiometer depth), mass loss over time, and derived unsaturated hydraulic conductivity and soil water‑retention characteristic.
- Data interpretation: Results produce retention curves and conductivity vs. matric head relationships for use in hydrological and agronomic models.
- Limitations and accuracy: The method yields data only for the drying path and has soil‑dependent measurable ranges; accuracy section and test reporting requirements are specified in the standard.
Applications
Who uses EN ISO 11275:2014 and why:
- Soil scientists and hydrologists assessing soil hydraulic properties for research or modelling.
- Agricultural engineers and irrigation planners estimating plant‑available water and drainage behavior.
- Environmental consultants performing pollution risk assessment, vadose‑zone transport studies, or remediation planning.
- Soil testing laboratories conducting standardized laboratory determinations of unsaturated hydraulic conductivity and water‑retention curves.
Practical uses include pore‑size distribution assessment, drainage design inputs, monitoring soil structural changes (compaction, amendment effects), and supporting numerical flow models.
Related Standards
Relevant referenced documents (normative or complementary):
- ISO 10381‑1 / ISO 10381‑4 - soil sampling guidance.
- ISO 11274 - laboratory methods for water‑retention characteristic (wider matric head range).
- ISO 11276 - tensiometer method for pore water pressure.
- ISO 11461 - gravimetric water‑content determination.
Keywords: EN ISO 11275:2014, Wind's evaporation method, unsaturated hydraulic conductivity, water‑retention characteristic, soil quality, matric head, tensiometer, laboratory method.
