  We present a systematic study of electron backscattering phenomena during
conduction for graphene nanoribbons with single-vacancy scatterers and
dimensions within the capabilities of modern lithographic techniques. Our
analysis builds upon an \textit{ab initio} parameterized semiempirical model
that breaks electron-hole symmetry and nonequilibrium Green's function methods
for the calculation of the conductance distribution $g$. The underlying
mechanism is based on wavefunction localizations and perturbations that in the
case of the first $\pi-\pi{}^*$ plateau can give rise to impurity-like
pseudogaps with both donor and acceptor characteristics. Confinement and
geometry are crucial for the manifestation of such effects. Self-consistent
quantum transport calculations characterize vacancies as local charging centers
that can induce electrostatic inhomogeneities on the ribbon topology.
