  Gas plays a major role in the dynamical evolution of protoplanetary discs.
Its coupling with the dust is the key to our understanding planetary formation.
Studying the gas content is therefore a crucial step towards understanding
protoplanetary discs evolution. Such a study can be made through spectroscopic
observations of emission lines in the far-infrared, where some of the most
important gas coolants emit, such as the [OI] 3P1-3 P2 transition at 63.18
microns. We aim at characterising the gas content of protoplanetary discs in
the intermediate-aged Chamaeleon II (Cha II) star forming region. We also aim
at characterising the gaseous detection fractions within this age range, which
is an essential step tracing gas evolution with age in different star forming
regions. We obtained Herschel-PACS line scan spectroscopic observations at 63
microns of 19 Cha II Class I and II stars. The observations were used to trace
[OI] and o-H2O at 63 microns. The analysis of the spatial distribution of [OI],
when extended, can be used to understand the origin of the emission. We have
detected [OI] emission toward seven out of the nineteen systems observed, and
o-H2O emission at 63.32 microns in just one of them, Sz 61. Cha II members show
a correlation between [OI] line fluxes and the continuum at 70 microns, similar
to what is observed in Taurus. We analyse the extended [OI] emission towards
the star DK Cha and study its dynamical footprints in the PACS Integral Field
Unit (IFU). We conclude that there is a high velocity component from a jet
combined with a low velocity component with an origin that may be a combination
of disc, envelope and wind emission. The stacking of spectra of objects not
detected individually in [OI] leads to a marginal 2.6sigma detection that may
indicate the presence of gas just below our detection limits for some, if not
all, of them.
