  We present results from a non-cosmological, three-dimensional hydrodynamical
simulation of the gas in the dwarf spheroidal galaxy Ursa Minor. Assuming an
initial baryonic-to-dark-matter ratio derived from the cosmic microwave
background radiation, we evolved the galactic gas distribution over 3 Gyr,
taking into account the effects of the types Ia and II supernovae. For the
first time, we used in our simulation the instantaneous supernovae rates
derived from a chemical evolution model applied to spectroscopic observational
data of Ursa Minor. We show that the amount of gas that is lost in this process
is variable with time and radius, being the highest rates observed during the
initial 600 Myr in our simulation. Our results indicate that types Ia and II
supernovae must be essential drivers of the gas loss in Ursa Minor galaxy (and
probably in other similar dwarf galaxies), but it is ultimately the combination
of galactic winds powered by these supernovae and environmental effects (e.g.,
ram-pressure stripping) that results in the complete removal of the gas
content.
