Gauge Köln is on the Rhine at kilometre 688, on the km 660–710 stretch. The GlW is 139 cm and the fairway depth maintained below it (TuGlW) is 250 cm; after deducting 30 cm of safety margin the official rule of thumb comes out at Köln +81. In practice Köln +80 is used here, -1 cm against the official rule. At high water Marke I is at 620 cm and Marke II — above which the waterway closes — at 830 cm. This gauge has 4 forecast sources: the 4-day forecast from Elwis (green), the 2-day forecast from the Hochwasserzentrale Rheinland-Pfalz (red), the 14-day forecast from the BAfG (yellow) and the 6-week forecast from the BAfG (blue, set the time range to 6 weeks to see it). Upstream lies Bonn, downstream Düsseldorf.
Cologne
The shoal at Cologne is the biggest bottleneck for ships sailing to e.g. the Moselle. The 'Deutzer Platte' lies between the Deutzer Brücke and the Severinsbrücke across the full width of the fairway; there is no real way around it. Officially, the bottom here should be at Cologne Gauge + 111 cm, but there are regularly 'Fehltiefen' (depth deficits). See also Elwis Shallow Depths (unfortunately not very clear, but that's the best available in Germany). According to the Bottleneck Profile, the latest soundings are published via the Depth Atlas, however, this has not happened since 2020 so it is nothing more than an empty promise... See also the depth charts of the Dutch and German Rhine branches on pdf v20-08-2026.