H₂O photodissociation timescale and turbulent diffusion mixing timescale of the fiducial model using the chemical network. The 1,10 and 100 year timescale contours are indicated in white in both panels. The dark blue contours in both panels indicate the 10⁻⁵, 10⁻⁶, and 10⁻⁸ H₂O abundance contours of the fiducial chemistry model (see also top left panel of Fig. 1). The light blue line represents the H₂O snow surface.