Two long Nordic river records, moving in opposite directions

Both publishers compute the daily value themselves, from their own measurement and their own rating curves, and Hydrionis stores the number they publish. Nothing here is a mean Hydrionis derived.

Sweden’s archive is the better known and reaches back further as a network: 1851 against Finland’s 1847. The deepest single record is Finnish. Muroleenkoski has been gauged since 1863 and holds 59,772 measured days across 164 years, against 50,273 days over 138 years at ÖVRE HYNDEVAD, the deepest Swedish record.

50,273 measured days, 100% of the days in its own span, in the NORRSTRÖM basin. Decades are drawn only where at least 3,000 days are held, so a decade missing from the chart is a gap in the record rather than a gap in the river.

59,772 measured days, 100% of the days in its own span, in the Kokemäenjoki basin. Decades are drawn only where at least 3,000 days are held, so a decade missing from the chart is a gap in the record rather than a gap in the river.

The Swedish record falls by 20 per cent between its first three decades and its last three. The Finnish record over a longer span rises by 8 per cent. Neither figure is small, and they point opposite ways.

The final column is why neither should be read as a trend. At both gauges the gap between the wettest decade on record and the driest is several times the difference between the record’s two ends. A century of daily measurement at one gauge describes that gauge very well and settles nothing about direction.

• Finland Historical River Discharge Dataset v1.0.0 · 10,327,195 observations
• Sweden Historical River Discharge Dataset v1.0.0 · 9,507,623 observations

Every figure above is computed from these datasets at build time rather than written into the text. If the underlying record changes, this page changes with it.