Abstract
Generally, the calculated discharge is an output that passes through two low pass filters, a discrete system and a runoff system. A discrete system accumulates the real rainfall which is continuous over a period of time, Δt. The output from the discrete system is an input to runoff system described by runoff models. The optimal time interval, Δt, depends on a runoff system or mainly basin scale. In this paper, we adopt Kinematic Wave equation and two kinds of storage function runoff models derived from Kinematic Wave equation as runoff models and introduce an extended frequency response method to evaluate the optimum time interval, Δt.
