Predictions of the p-H₂O 3₁₃ − 2₂₀ line intensity, in units of brightness temperature, for gas with density n(H₂) in the range 10³ − 10⁸cm^-3, temperature in the range 50 − 200   K, for column densities of para-water equal to 0.003 (bottom curve), 0.01, 0.03, 0.1, 0.3, 1.0 × 10¹⁹cm^-2 (top curve). The range of T_B − n(H₂) determined in the water-emitting clumps is delineated by rectangles.