  We study the effect of non-vanishing masses and mixings among neutrino
flavours on the detection of neutrinos from stellar collapse by a water
Cerenkov detector. We consider a realistic framework in which there are three
neutrino flavours whose mass squared differences and mixings are constrained by
the present understanding of solar and atmospheric neutrinos. We also include
the effects of high dense matter within the supernova core. We find that the
number of events due to the dominant process involving electron-antineutrinos
may change dramatically for some allowed mixing parameters. Furthermore,
contributions from charged-current scattering off oxygen atoms in the detector
can be considerably enhanced due to flavour mixing; such events have a distinct
experimental signature since they are backward-peaked. Hence, mixing has a
non-trivial effect on the signature of neutrinos (and antineutrinos) from
stellar collapse.
