The density of the water-sediment mixture is calculated with the following constitutive equation:

\rho_m = \rho_w + (\rho_s - \rho_w) C_v

where \rho_wis the water density, \rho_sis the particle density, and C_v volumetric concentration between 0 and 1. The above equation assumes that all of the voids between the particles are occupied water and that there is no air in the mixture.