  Ro-vibrational absorption lines of H$_2$O in the 5-8 $\mu$m wavelength range
selectively probe gas against the mid-infrared continuum emitting background of
the inner regions of YSOs and AGN and deliver important information about these
warm, dust-obscured environments. JWST/MIRI detects these lines in many lines
of sight at a moderate spectral resolving power of $R\sim3500$ (FWHM of 85
km/s). Based on our analysis of high-resolution SOFIA/EXES observations, we
find that the interpretation of JWST/MIRI absorption spectra can be severely
hampered by the blending of individual transitions and the lost information on
the intrinsic line width or the partial coverage of the background continuum
source. In this paper, we point out problems such as degeneracy that arise in
deriving physical properties from an insufficiently resolved spectrum. This can
lead to differences in the column density by two orders of magnitude. We
emphasize the importance of weighting optically thin and weak lines in spectral
analyses and provide recipes for breaking down the coupled parameters. We also
provide an online tool to generate the H$_2$O absorption line spectra that can
be compared to observations.
