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These plots monitor Rhine water level as it passes through Bonn and put it in historical context....

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Twenty lowest daily water levels at Bonn, on the current gauge zero (1960–2026):

#	Date	Level (cm)	Clim. mean	Anomaly
1	2026-08-07	75	253.2	−178.2
2	2026-08-10	75	253.4	−178.4
3	2026-08-06	77	254.2	−177.2
4	2026-08-08	77	252.8	−175.8
5	2026-08-09	78	252.9	−174.9
6	2026-08-01	80	263.7	−183.7
7	2018-10-22	81	225.1	−144.1
8	2018-10-23	81	226.2	−145.2
9	2026-08-03	81	259.0	−178.0
10	2018-10-25	82	229.1	−147.1
11	2026-07-31	82	266.2	−184.2
12	2018-10-21	83	224.6	−141.6
13	2018-10-29	83	238.4	−155.4
14	2026-07-29	83	271.4	−188.4
15	2026-08-02	83	261.3	−178.3
16	2026-08-04	83	257.2	−174.2
17	2026-08-05	83	255.6	−172.6
18	2018-10-24	84	227.6	−143.6
19	2018-10-28	84	235.7	−151.7
20	2022-08-16	84	252.8	−168.8

Only three years appear — 2018, 2022 and 2026 — and 2026 holds 11 of the 20, including the record low of 75 cm, reached twice in the last ten days of data.

Two points worth noting:

None fall before November 1979, so the datum correction doesn't affect this ranking at all. It would have mattered: on the uncorrected data the pre-1979 readings sat a metre low, and several would have crowded into this table as spurious record lows.

The 2026 events are more extreme than their raw levels suggest. The 2018 dates occur in late October when the climatological mean is ~225 cm, whereas the 2026 dates fall in late July and August when it's ~255–270 cm. So 2026 sits roughly 175–188 cm below normal against 142–155 cm in 2018 — a deeper departure, not merely a similar level at a different time of year. On the interactive page these days sit below the P01 line, which for that time of year is around 124 cm.

Twenty most negative daily anomalies at Bonn (1960–2026):

#	Date	Anomaly	Level	Clim. mean	P01	Below P01
1	2017-01-10	−266.5	117	383.5	124	yes
2	2017-01-09	−266.2	118	384.2	124	yes
3	2017-01-08	−263.9	120	383.9	123	yes
4	2017-01-03	−260.9	123	383.9	125	yes
5	2017-01-04	−260.3	124	384.3	124	no
6	1963-03-04	−260.2	116	376.2	198	yes
7	2017-01-02	−259.4	124	383.4	125	yes
8	1963-03-05	−259.0	116	375.0	197	yes
9	2017-01-11	−258.8	123	381.8	124	yes
10	2017-01-01	−258.6	125	383.6	126	yes
11	2017-01-05	−258.5	126	384.5	124	no
12	2017-01-07	−258.4	125	383.4	123	no
13	1963-03-03	−258.3	118	376.3	198	yes
14	1963-03-02	−256.3	119	375.3	201	yes
15	2016-12-31	−255.6	129	384.6	126	no
16	2017-01-06	−255.6	128	383.6	123	no
17	1963-02-12	−254.6	111	365.6	149	yes
18	1963-03-06	−253.8	121	374.8	194	yes
19	2016-12-29	−253.5	132	385.5	131	no
20	2016-12-30	−253.4	132	385.4	127	no

A completely different list from the lowest levels — no overlap at all. These are two clusters: the 2016/17 New Year period (14 days) and late winter 1963 (6 days). All fall in December–March, when the climatological mean is at its seasonal peak near 385 cm, so a level of ~120 cm produces a −260 cm departure. The record-low levels of 2018/2022/2026 don't appear here because they occur in late summer, when the mean is only ~225–270 cm, capping the possible departure.

Put plainly: the lowest levels are summer events, the largest anomalies are winter events. August 2026 set the absolute record at 75 cm; January 2017 was further from normal despite standing 40 cm higher.

Two things worth noting:

Six of these are pre-1979 and depend on the correction we just applied. On the uncorrected data those 1963 days would have shown anomalies near −360 cm and dominated the entire ranking — a pure artefact. They're still genuinely extreme after correction, just not record-breaking.

The 1963 P01 values look odd next to 2017's — around 198 cm for early March against ~124 cm for early January. That isn't an error: the percentiles come from the 1990–2021 climatology, which has a much higher 1st percentile in March than in January. It does mean the 1963 days sit far below their seasonal P01 while several 2017 days sit just above theirs, which is why the "below P01" column disagrees with the anomaly ranking in places.