A new method is presented for modelling three-dimensional turbulent di
spersion problems in.open channels with an arbitrary, but uniform, cro
ss-section. The semi-analytical technique is applicable when investiga
ting the steady discharge of effluent into a channel which has distrib
utions of longitudinal velocity and turbulent diffusivities specified
over its cross-section. Implementation of the method is discussed, alo
ng with an example illustrative of the effects of three-dimensional mi
xing. Predictions are also compared with the experimental results of W
ood and Liang (1989) for mixing in a flood-plain/main channel geometry
.