“…Water level flow in open channels. By applying a diffusion wave approximation to the Saint-Venant equations, it is well known ANTONTSEV, and MEIRMANOV, 1977b;DALUZ VIEIRA, 1983;EPIKHOV, 1985;KUCHMENT et al, 1983;VASILIEV, 1987 and their references) that if we denote by u(s, t) to the water level in the channel stream, by x to the cross-sectional area (x u = qx/qu = B is the width) and to s to the channel curvilinear length variably measured along its axial cross section, then we arrive at the nonlinear parabolic equation where w(s,u) = Cx R 2/3 is the discharge modulus, C is the coefficient Chezy, R is the hydraulic radius, f P is a source function,…”