Hydraulic Properties of Unsaturated Soils
Summary
Unsaturated soils occupy the zone between the water table and the ground surface, where capillary and gravitational forces govern the distribution and movement of water. Their hydraulic properties—principally the soil water retention curve and unsaturated hydraulic conductivity—control water storage, infiltration, redistribution and evapotranspiration in the critical zone. These properties are determined by intrinsic soil factors such as texture, structure, bulk density and organic matter content, and are further complicated by dynamic processes such as hysteresis between wetting and drying paths and deformation of pore architecture. Mathematical descriptions of retention and flow often employ parametric models, including van Genuchten–Mualem formulations and more recent modular frameworks that partition capillary and noncapillary contributions. Robust prediction of soil hydraulic behaviour underpins applications in agriculture, civil engineering and water resource management, from slope stability and irrigation scheduling to groundwater recharge estimation and climate-resilient land use.
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Hydraulic Properties of Unsaturated Soils publication trend
The graph below shows the total number of articles in hydraulic properties of unsaturated soils across all publications each year (not limited to Nature Index journals).
Technical terms
Unsaturated soil: Soil that contains both air and water in its pore space, lying above the groundwater table.
Soil water retention curve (SWRC): Relationship between soil water content and matric suction, depicting how water is held in soil pores.
Hydraulic conductivity: Measure of a soil’s ability to transmit water under a hydraulic gradient.
Matric suction: Negative pressure in the soil pore water caused by capillary and adsorptive forces.
Air-entry value: The matric suction at which air begins to displace water from the largest pores.
Hysteresis: Dependence of the soil water retention curve on the wetting or drying history of the soil.
Pedotransfer function: Empirical relationship used to estimate hydraulic parameters from readily measured soil properties.
References
- Soil water retention and hydraulic conductivity measured in a wide saturation range. Earth System Science Data (2023).
- Machine learning-based estimation of soil’s true air-entry value from GSD curves. Gondwana Research (2023).
- A Modular Framework for Modeling Unsaturated Soil Hydraulic Properties Over the Full Moisture Range. Water Resources Research (2019).
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