  We analyzed V-band photometry of the Be star {\omega} CMa, obtained during
the last four decades, during which the star went through four complete cycles
of disc formation and dissipation. The data were simulated by hydrodynamic
models based on a time-dependent implementation of the viscous decretion disc
(VDD) paradigm, in which a disc around a fast-spinning Be star is formed by
material ejected by the star and driven to progressively larger orbits by means
of viscous torques. Our simulations offer a good description of the photometric
variability during phases of disc formation and dissipation, which suggests
that the VDD model adequately describes the structural evolution of the disc.
Furthermore, our analysis allowed us to determine the viscosity parameter
{\alpha}, as well as the net mass and angular momentum (AM) loss rates. We find
that {\alpha} is variable, ranging from 0.1 to 1.0, not only from cycle to
cycle but also within a given cycle. Additionally, build-up phases usually have
larger values of {\alpha} than the dissipation phases. Furthermore, during
dissipation the outward AM flux is not necessarily zero, meaning that {\omega}
CMa does not experience a true quiescence but, instead, switches between a high
to a low AM loss rate during which the disc quickly assumes an overall lower
density but never zero. We confront the average AM loss rate with predictions
from stellar evolution models for fast-rotating stars, and find that our
measurements are smaller by more than one order of magnitude.
