  We observed the Seyfert 1 galaxy Mrk817 during an intensive multi-wavelength
reverberation mapping campaign for 16 months. Here, we examine the behavior of
narrow UV absorption lines seen in HST/COS spectra, both during the campaign
and in other epochs extending over 14 years. We conclude that while the narrow
absorption outflow system (at -3750 km/s with FWHM=177 km/s) responds to the
variations of the UV continuum as modified by the X-ray obscurer, its total
column density (logNH =19.5 cm-2) did not change across all epochs. The
adjusted ionization parameter (scaled with respect to the variations in the
Hydrogen ionizing continuum flux) is log UH =-1.0. The outflow is located at a
distance smaller than 38 parsecs from the central source, which implies a
hydrogen density of nH > 3000 cm-3. The absorption outflow system only covers
the continuum emission source and not the broad emission line region, which
suggests that its transverse size is small (< 1e16 cm), with potential cloud
geometries ranging from spherical to elongated along the line of sight.
