Comparison between the integrated intensity maps of 988 GHz H₂O in gray and CN(2–1) (contours, Martín et al. 2012). The integrated velocity range of the H₂O map is [−180,140] km s⁻¹. The wedge at the right shows the H₂O intensity gray scale in K km s⁻¹. Crosses and their numbers show positions, where spectra used in the kinematic study were extracted over the 22′′ beam. Thesepositions correspond to selected CN(2–1) and H₂CO(3₃₀–2₂₀) emission peaks on the CND (Martín et al. 2012). The white star shows the position of Sgr A^* and origin of the offsets. The HIFI beam of 22′′ at 988 GHz is shown in the left corner. Contour levels of the CN map start at 3σ and increase in 4σ steps. Blue circles with a size of 22′′ show the CND₁ and CND₂ positions selected for our study of the water excitation (see Sect. 5). The CND₁ and CND₂ positions were observed towards the southwest and northeast lobes, respectively, of the CND (Requena-Torres et al. 2012).