  Hydrogeodesy can benefit greatly from the use of Global Positioning System
(GPS) displacements to analyse local changes in the hydrosphere, which the
commonly used Gravity Recovery and Climate Experiment (GRACE) mission is unable
to provide due to coarse spatial resolution. Hydrosphere changes recorded by
GPS are unfortunately hidden among the other signals to which the system is
also sensitive so that the sensitivity of GPS to changes in the hydrosphere on
temporal-scales from pluri-annual to decadal is questionable. We focus on
hydrosphere signatures present on these long-term temporal-scales as observed
by GPS through the vertical displacement time series (DTS) of 122 permanent
stations over Europe and compare them to the DTS derived from GRACE for GPS
locations. Our methodology is based on the weighted Savitzky-Golay (S-G)
filter, an underestimated filter in the field of geodetic time series analysis.
We show that the correspondence between GPS and GRACE on long-term
temporal-scales is generally strong, but decreases for coastal regions and
regions where the coarse gridding of GRACE does not capture local hydrosphere
effects. Further, the negative correlation with El Ni\~no Southern Oscillations
(ENSO) is confirmed for Europe.
