Water Retention and Characteristic Curve

A soil-water characteristic (SWC) curve describes the amount of water retained in a soil (expressed as mass or volume water content, m or v) under equilibrium at a given matric potential. An SWC is an important hydraulic property, related to size and connectedness of pore spaces, hence strongly affected by soil texture and structure, and by other constituents, including organic matter. Modeling water distribution and flow in partially saturated soils requires knowledge of the SWC, therefore plays a critical role in water management and in prediction of solute and contaminant transport in the environment. Typically a SWC is highly nonlinear and is relatively difficult to obtain accurately. Because the matric potential extends over several orders of magnitude for the range of water contents commonly encountered in practical applications, the matric potential is often plotted on a logarithmic scale. Figure 1 depicts representative SWC curves for soils of different textures, demonstrating the effects of porosity (saturated water content) and