General
Water in the soil

We have seen in this treatise [4] that water can be found in several states inside a soil, depending on the intensity of the forces binding its molecules to solid particles (figure 1). A distinction is made between :

• water of constitution, which enters into the chemical composition of the minerals from which the soil particles are formed;

• bound or absorbed water, on the surface of very fine grains, which is oriented by molecular attraction and electrostatic forces; it has a high viscosity and does not transmit pressure;

• free water, which circulates freely in the soil pores under the effect...