## Physical Properties Of Water

The density of a material is defined as the mass per unit volume. The density (p) of water varies with temperature, pressure, and the concentration of dissolved materials and is about 1000 kg/m3. Multiplying p by the acceleration of gravity (g) gives the specific weight (y) as y ~ pg. For water, y « 9.8 kN/m3.

Some of the physical properties of water are defined as follows:

dynamic viscosity (p)—The ratio of shear stress (ryx) in x direction, acting on an x-y plane to velocity gradient (dvx/dy); Tyx = p dvx/dy. For water, p = 10~3 kg/m • s. kinematic viscosity (v)—Related to p by v = p/p. Its value is about 10~6 m2/s for water. compressibility (fi)—The ratio of change in density caused by change in pressure to the original density fi = __ dp = 1 dV p dp V dp fi « 0.5 X 10~9 m2/N 9.1(3)

The variation of density and viscosity of water with temperature can be obtained from Table 9.1.4.

Physical Properties of Vadose Zones and Aquifers

A description of the physical properties of vadose zones and aquifers follows.

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