Determining agricultural water demand from natural streams using the entropy concept

Abstract

Determining water flow discharge in open channels is a very important task for agricultural water 
management, but current methods are labor-intensive and difficult. The entropy method suggested by Chiu 
and Said (1995) promises to simplfy the task of measuring water flow rates. This paper offers a further 
simplification of ongoing discharge measurements by showing that the umax and Hmax values form a constant 
in a specific water channel cross section. Once the umax/Hmax constant is determined, umax, and therefore 
discharge, can easily be calculated from Hmax measurements. This method, which we call Qumax method in this 
paper, was compared against the integrated discharge method for accuracy and was found to have an 
accuracy similar to that of two other common methods, the integrated Q 0.2 to 0.8 and the entropy methods 
(QMi). Comparisons were carried out at four sites along the tributaries of the Kizilirmak river in central 
Anatolia, Turkey.