Left: intensity profile normalized to 0.′′75 beam of the HO 3_1,3–2_2,0 203 GHz (light blue line) and dust continuum using κ_{203 GHz} = 0.7 cm⁻² g⁻¹ (blue dashed line) for a power-law disk model with a water abundance of 10⁻⁴ with respect to H₂ when T_dust > 100 K (see text). The optical depth of the water line and the dust are shown in solid and dashed red lines, respectively. Horizontal and vertical grey lines indicate the optical depth of one and its location, respectively. These intensity profiles have not been convolved with the synthesized beams. Right: normalized intensity profile including the dust attenuation and dust continuum subtraction. Two dust opacities are used to illustrate the influence of the dust mass absorption coefficient on the emergence of the water line. Vertical lines indicate the radii where the dust optical depth is larger than unity for κ_ν = 0.7 cm² g⁻¹ (green) and κ_ν = 2 cm² g⁻¹ (blue) at 203 GHz. Shaded regions show the simplified effective emitting region due to dynamical limit (S∕N ~ 30 per velocity channel).