← Atlas catalogue · project 079

Trójmorski Wierch · the Polish–Czech borderland

On the watershed of two seas

At Trójmorski Wierch (Czech: Klepáč) three sea catchments meet, not two: those of the Baltic Sea, the Black Sea and the North Sea. Walk around the junction. One step sideways swaps the whole chain of rivers, and right at the divide the model admits that it cannot decide.

Without JavaScript you see the initial state: the point on side A and all three chains of rivers. Moving the point requires JavaScript; the explanation and sources are below.

Diagram of the junction of three sea catchments A diagram, not a map. Three orange watershed-divide lines meet at one junction and split the circle into three sea catchments: A for the Baltic Sea, B for the Black Sea and C for the North Sea. From each catchment a river arrow leads to the letter of its sea. A point moves around the circle centred on the junction; along each divide line a hatched band marks the area in which the model names no sea.
  • watershed divide
  • undecided band
  • point (empty = no sea)
A diagram, not a map. Three divide lines meet at the junction and split the circle into catchments A, B and C. The dots on the circle are the 36 positions of the point; 1 step = 10° of the diagram, not metres. The directions of the arms and the sizes of the sectors are conventional and do not follow the terrain. You can also place the point by clicking the diagram.

A step sideways

position 2 of 0–35
How precisely do we know the course of the divide?

This is an assumption of the model, not a measurement: the less certain the course of the divide, the wider the band in which no sea may be named.

Result: where the water from this point flows

Side A · Baltic Sea

Drainage on this side: Nysa Kłodzka → Oder → Szczecin Lagoon → Baltic Sea.

The nearest divide separates the Baltic Sea and Black Sea catchments and is 2 steps from here. Uncertainty band: ±1 step. To its edge: 1 step.

A

Baltic Sea

The point drains here
  1. Nysa Kłodzka
  2. Oder
  3. Szczecin Lagoon
  4. Baltic Sea

Nysa Kłodzka belongs to the Oder river basin (ZPE).

B

Black Sea

Away from the point
  1. Morava (Polish: Morawa)
  2. Danube
  3. Black Sea

The Morava is a left-bank tributary of the Danube; it joins it near Devín (Povodí Moravy).

C

North Sea

Away from the point
  1. Cicha Orlica (Tichá Orlice)
  2. Orlica
  3. Elbe (Labe)
  4. North Sea

The third direction. According to PIG-PIB, the Cicha Orlica is one of the rivers with their sources in this area; its chain leads via the Elbe to the North Sea. More.

The third direction is not a footnote

The Polish Geological Institute (PIG-PIB) describes this area as the source area of three rivers: the Nysa Kłodzka, the Cicha Orlica and the Morava. At Trójmorski Wierch (Klepáč) the catchments of the Baltic Sea, the North Sea and the Black Sea therefore meet. Source: PIG-PIB.

The title speaks of two seas because that is how many the comparison of the Oder and the Danube set side by side in the previous version of this page, which hid the third direction behind a button. Here chain C has the same row, colour and line pattern as the other two, because reducing this place to an either/or of two seas would be a mistake.

The intermediate links of chain C (Orlica, Elbe) were carried over from the previous version; they need to be checked again against the sources. Chains A and B are also shortened to the links from the supplied material and leave out tributaries.

Three concepts that hold the diagram together

A divide is not a river
A watershed divide separates the directions of drainage into different river basins. Do not look for a blue line running along the ridge: it is a boundary on whose two sides water may feed different river systems. On a trail you will not see it with the naked eye, because it is a high point of the terrain, not a ditch or a stream. ZPE
River basin and sea catchment
A river basin comprises a river together with its tributaries. A sea catchment combines the river basins that carry water to the same sea. That is why the Nysa Kłodzka belongs to the Oder river basin and, together with it, to the Baltic Sea catchment. ZPE
The Morava meets the Danube
The Czech Morava, in Polish Morawa, is a left-bank tributary of the Danube. It joins it near Devín, on the border of Slovakia and Austria. The plan of the water manager Povodí Moravy assigns its river basin to the Black Sea catchment. Povodí Moravy

What this diagram knows and what it does not

What it shows

  • A dependency: the same point on the other side of the divide belongs to a different chain of rivers and a different sea.
  • That close to the divide the diagram has no right to choose a sea. The absence of a decision is neither zero nor a fourth sea.
  • Three chains from the source material, all at once and described in the same way.

What it does not show

  • The actual course of the divide or any azimuths. Only a verified local map could show it, along with lawful vantage points; there is no such map here.
  • Distances: a step is 10° on the circle of the diagram, not metres. Nor are there droplet speeds or water travel times.
  • Groundwater and the influence of the bedrock: in the field water behaves according to the local relief and bedrock, not according to this drawing.
  • A route, navigation, or permission to enter a given area.

What is gone compared with V2

  • The numeric field and the scale from −100 to +100: they duplicated the slider. They were replaced by 36 positions on the circle.
  • Five scenario buttons and the “±35 reflection”: they were replaced by step back and step forward and by the buttons on the catchment cards.
  • The fixed ±2 band: the width of the uncertainty is now a choice, because it is precisely the assumption.
  • The field notebook: it did not explain the relationship. V3 saves nothing in the browser; any V2 entries (key atlas-v2-79) remain, and V3 neither reads nor deletes them.
  • A photograph fetched from the internet: the page works offline, and the photo is only a link in the sources.

Sources and verification status

The links were carried over from the previous version. In V3 they were not reopened or verified again; every element of the river chains and the descriptions beside individual sources need to be checked by the editors. This is not expert testimony.

  1. PIG-PIB: nowy transgraniczny projekt badawczy, badanie ekosystemu wodnego w przełomie kłodzkim [new cross-border research project on the aquatic ecosystem in the Kłodzko Gorge] Used for: the sources of the Nysa Kłodzka, the Cicha Orlica and the Morava; the meeting of three sea catchments. To check: the Orlica and Elbe links in chain C.
  2. Zintegrowana Platforma Edukacyjna: rozmieszczenie zlewisk i dorzeczy [Integrated Educational Platform: distribution of sea catchments and river basins] Used for: definitions of river basin, sea catchment and divide; Nysa Kłodzka, Oder, Baltic Sea. To check: Szczecin Lagoon as a link in chain A.
  3. Povodí Moravy: river basin plan 2021–2027 Used for: the Morava, the Danube, the confluence near Devín, the Black Sea. To check: the description of the Slovak–Austrian border.
  4. RCIN: Północno-wschodnia Europa pod względem hydrograficznym [RCIN: North-eastern Europe from the hydrographic point of view] Historical background on the great watershed divides of Europe; in V3 it is not used as evidence for any sentence on the page.
  5. Główny Urząd Geodezji i Kartografii: Numeryczny model terenu [Head Office of Geodesy and Cartography: Digital terrain model] A methodological reference: the course of ridges is derived from such data. This diagram does not use them.
  6. Photograph of Trójmorski Wierch on Wikimedia Commons, author Jacek Halicki, licence CC BY-SA 4.0 (according to the V2 description) The previous version displayed this photograph; V3 does not load it and gives only the link. The licence and authorship were not checked again.