RELIABILITY OF STEADY SURFACE PROFILE IN IRRIGATION CANAL

A reliability problem in irrigation canal systems where the water dema nd fluctuates stochastically is examined. A dow model of open channel with control structures is developed to include the lateral withdrawal , in which the flow rate is suddenly changeable temporally and spatial ly. Discussion is focussed on the propriety of a steady dow surface pr ofile for an averaged water demand pattern. Assuming that the temporal evolution of unsteady flow surface profile is a Markov process, the t heory of statistics is applied. Since the probability density function is governed by the Fokker-Planck partial differential equation, evalu ating the reliability that the disturbance of surface profile around t he steady state is small enough, is reduced to solving the heat equati on deduced from a geometrical consideration. The acquired concept is a pplied to the design problem of a reliable steady surface profile. Com putations are performed through roughly two stages, i.e., the approxim ation of the diffusion tensor that constitutes the coefficient matrix of the governing equation using the how model and the diagonalization of the diffusion tensor.