Left figure: averaged and normalised spectrum calculated for the low-mass Class 0 (LM0) protostars, the low-mass Class I (LMI), intermediate-mass YSOs (IM) and high-mass objects (HM) for the H₂O 2₀₂–1₁₁ 988 GHz (left panel), 2₁₁–2₀₂ 752 GHz (middle-left panel), 3₁₂–3₀₃ 1097 GHz (middle-right panel) transitions and the ¹²CO J = 10–9 (right panel) spectra (see San José-García et al. 2013). The spectra of each sub-group of YSOs have been shifted vertically for visualisation purposes. The low intensity features on the blue wing of the H₂O 2₁₁–2₀₂ high-mass profile are due to methanol emission. Right figure: H₂O 2₀₂–1₁₁, 2₁₁–2₀₂ and 3₁₂–3₀₃ spectra plotted in red, blue and purple respectively for NGC 1333 IRAS4B (LM0), GSS 30 (LMI), NGC 2071 (IM) and W33A (HM). The horizontal light green lines in both figures represent the baseline level.