Discussion of "Inlet Pressure, Energy Cost, and Economic Design of Tapered Irrigation Submains" by John D. Valiantzas

The discussers wish to thank the author for obtaining a new technique, based on the analytical approach recently presented by Valiantzas (2002b), to calculate directly the economic design problem of multioutlet submain lines. In the previous study, analytical procedures were based only on hydraulic design criteria, whereas in this suggested economic design procedure, the energy cost is only taken into account; in other words, hydraulic uniformity constraints along the submain line are not considered. The author has reported that direct design solutions were obtained for the economic design problem of a multioutlet submain line. However, it may be very hard to obtain analytical equations which provide direct general solutions of multioutlet submains, especially for the relationship between outlet discharge and pressure head, which is nonlinear. In the following analysis, the discussers would like to present important points of view that the authors and potential readers need to consider.