We present a numerical assessment of coupling conditions in T-junction for water flow in open canals. The mathematical model is based on the well-established shallow water equations for open channel flows. In the present work, the emphasis is given to the description of coupling conditions at canal-to-canal intersections. The accurate prediction of these coupling conditions is essential in order to achieve good performance and reliable numerical simulations of water canals in networks. There exist several theoretical results for coupling conditions in a reduced geometry. The purpose of our work is to numerically verify these conditions for different water flow regimes. More precisely, we consider a local zooming of the T-junction resulting in a two-dimensional flow problem at the canals intersection. A high-order non-oscillatory method is used for solving the governing two-dimensional equations, and the water flow solutions are space-averaged over the junction areas. The obtained are thereafter, used for verification and comparison with the theoretical results. Verifications are conducted for two types of junctions, namely the 1-to-2 and 2-to-1 situations. Copyright © 2012 John Wiley & Sons, Ltd.