  Damped Lyman-alpha absorbers are believed to be associated with galactic
disks. We show that gravitational lensing can therefore affect the statistics
of these systems. First, the magnification bias due to lensing raises faint
QSOs above a given magnitude threshold and thereby enhances the probability for
observing damped absorption systems. Second, the bending of light rays from the
source effectively limits the minimum impact parameter of the line-of-sight
relative to the center of the absorber, thus providing an upper cut-off to the
observed neutral hydrogen (HI) column density. The combination of these effects
yields a pronounced peak in the observed abundance of absorbers with high
column densities (>2*10^{21} cm^{-2}) and low redshifts (z<1). The inferred
value of the cosmological density parameter of neutral hydrogen, Omega_{HI},
increases with increasing redshift and luminosity of the sources even if the
true HI density remains constant. This trend resembles the observed evolution
of Omega_{HI}(z). Damped Lyman-alpha absorbers with column densities >10^{21}
cm^{-2} and redshifts 0.5<z<1 are reliable flags for lensed QSOs with a close
pair of images separated by 0.3 arcsec. Detection of these gravitational
lensing signatures with the Hubble Space Telescope can be used to constrain the
depth of the absorber potential-wells and the cosmological constant.
