  The supernova model discrimination capabilities of the WATCHMAN detector
concept are explored. This cylindrical kilotonne-scale water Cherenkov detector
design has been developed to detect reactor antineutrinos through inverse
$\beta$-decay for non-proliferation applications but also has the ability to
observe antineutrino bursts of core-collapse supernovae within our galaxy.
Detector configurations with sizes ranging from 16 m to 22 m tank diameter and
10% to 20% PMT coverage are used to compare the expected observable
antineutrino spectra based on the Nakazato, Vartanyan and Warren supernova
models. These spectra are then compared to each other with a fixed event count
of 100 observed inverse $\beta$-decay events and a benchmark supernova at 10
kpc distance from Earth. By comparing the expected spectra, each detector
configuration's ability to distinguish is evaluated. This analysis then
demonstrates that the detector design is capable of meaningful event
discrimination (90+% accuracy) with 100 observed supernova antineutrino events
in most configurations. Furthermore, a larger tank configuration can maintain
this performance at 10 kpc distance and above, indicating that overall target
mass is the main factor for such a detector's discrimination capabilities.
Finally, it is estimated that the detector design can provide early warning
capability for supernova bursts for the entire Milky Way in all configurations.
