Discussion of "Explicit Hydraulic Design of Microirrigation Submain Units with Tapered Manifold and Laterals" by John D. Valiantzas

The discussers would like to express their appreciation to the author for obtaining a new design technique based on the previous analytical approach presented by Valiantzas (2002) to calculate explicitly the optimum hydraulic design problem of microirrigation submain lines. In the recent study (Valiantzas 2003) the total (capital and operational) cost is only taken into account (hydraulic design constraints are not considered), whereas in the suggested economic design procedure, operational cost is not considered and the capital cost is minimized subject to meeting hydraulic uniformity constraints. The discussers consider that the following derivative correction in the paper should be made.