Alternative Method to the Clément’s First Demand Formula for Estimating the Design Flow Rate in On-Demand Pressurized Irrigation Systems

Abstract

It has been well documented in specialized literature that, under certain circumstances, the Clément’s first demand formula fails in estimating flow in water distribution networks. Through numerical examples, the authors show that the method fails when the number of hydrants supplied by a pipe is small or when the nominal flow rate of the hydrants is nonhomogeneous. In such cases, the normality hypothesis of the design flow rate random variable, an assumption needed by Clément’s formula, cannot be made. An alternative method for calculating the design flow rate as a nonnormal random variable is presented. The method works very well in all analyzed examples, mainly because the normality hypothesis is not required. The paper also provides a free-software R-script using freely available software that allows applying the proposed method to user-defined cases. The script helps to understand the method’s theoretical basis and can be used as a tool for checking the assumption of normality of data. Therefore, the program allows the applicability of Clément’s method to be checked and provides an alternative accurate solution.