Methodology

Where the numbers come from

• Water levels (cm) come from PEGELONLINE, published by the Wasserstrassen- und Schifffahrtsverwaltung des Bundes (WSV). We poll each gauge and store a reading every 30 minutes.
• Reference marks — MNW, MW, MHW, GlW, TuGLW, HSW, NNW, HHW and gauge zero — are official WSV values. We republish them, we never recompute them.
• Navigable (fairway) depth is the maintained fairway depth at the low-water reference (TuGLW) adjusted for today's reading relative to GlW. It describes the fairway, not clearance for any particular ship.
• 30-day average, low and high come from our own archive of 30-minute readings — not from any third party.
• Trend compares the latest reading with recent readings from the same gauge: rising, steady or falling. When we cannot determine it, we say so.

How the status words are decided

Each gauge is compared with its own official reference marks, so the same word means the same thing at every gauge:

• High water — the reading is at or above the highest navigable level (HSW).
• Good — the reading is at or above mean water (MW).
• Below normal — between mean low water (MNW) and mean water (MW).
• Low — below mean low water (MNW) but above the low-water navigation reference (GlW).
• Very low — at or below the low-water navigation reference (GlW).
• Unknown — the gauge is silent, or a reference mark needed for the comparison is not published. We show "not available".

Alongside our label we always show PEGELONLINE's own classification of the same reading, so you can see two independent readings of the same number.

What we do not do

• We publish measured conditions, not forecasts. There is no prediction of tomorrow's level anywhere on this site.
• We never predict what an operator will do. Ship swaps, reroutes and coach transfers are decisions made by the cruise line and the captain.
• When a gauge has sent nothing for six hours or more we mark it stale and show the time of its last reading. A stale reading is never presented as current.
• When a value is missing we print "not available" and say why. We never substitute a default, an estimate or an average.

Who publishes this

This tracker is published by RiverCruise.ai, powered by FlyOver Travel, a licensed travel agency. Gauge data is used under DL-DE-Zero-2.0. Feed health is published openly on our status page.