Predicted H₂O column density in the region where T_gas ≥ 150 K, for different initial distributions of nitrogen (columns) and sublimating ices (rows). T_gas ≥ 150 K is the temperature range probed by the Herschel PACS observations. Horizontal black dotted lines indicate the upper limit on the H₂O column density derived from the observations at 150 and 200 K. All models overpredict the upper limit on the H₂O column density. This could be due to optically thick dust at 51 − 220 μm hiding part of the H₂O column in the IRS 48 disk.