To illustrate the operational use of the micro-computer package DUFLOW for the simulation of one-dimensional unsteady flow in channel systems the tidal propagation in an irrigation system (IRRSYS) is considered. The propagation of periodical shallow water waves in a network system (tidal waves in river systems, estuaries, etc. and also harbor oscillations - "seiches" with periods of 5 till 60 minutes) has to be studied frequent1y in hydraulic and environmental engineering. The open channel system IRRSYS is based on existing tidal irrigation systems which are constructed in a large number for example in Sumatra and Kalimantan in Indonesie (Ref. [1] and Ref. [2]). Analog simulations of tidal propagation in sea area, lagoons, swamps, etc. can be characterized by a relatively large internal storage area combined with a narrow tidal inlet. In the Netherlands the tidal propagation in the Scheldt Rhine Ganal System (October 1986 until March 1987, see scheme in Figure 1 on page 2) can be characterized as analogous to the tidal propagation in IRRSYS, which wil1 be illustrated in Ghapter 5. The system IRRSYS is representative for many systems in other countries. The DUFLOW analysis of IRRSYS in relation with analytic solutions (Ref. [2] and [3]) and with results of measurements (Ref. [4]) is very useful to study some general aspects of tidal propagation.