Czech language distinguishes between larger (river) and smaller (stream, creek, brook etc.) watercourses; the respective nouns being řeka (feminine, "river") and potok (masculine, "stream"). River names are mostly self-standing nouns and not accompanied with the generic word for river (except when confusion might arise because the name is shared with some towns, e.g. Jihlava; in such cases one sometimes says řeka Jihlava).
In contrast, stream names mostly consist of two words because they contain an adjective (usually stemming from physical properties (e.g. Černý potok-"Black Stream"), usage (e.g. Mlýnský potok – "Mill Stream") or derived from the location through which it flows (e.g. Rakovnický potok-"Rakovník Stream")). These two-word names are used as a whole, the word potok making an inseparable part of the name (i.e. Mlýnský potok, not just Mlýnský). There are also streams with one-word names (either masculine or feminine) akin to rivers (e.g. Botič or Modla) but they are simply considered streams due to their small size. In such cases the word potok is optional and precedes the name (potok Modla).
Drainage basins
As the Main European Watershed passes through the Czech Republic, there are three directions and principal areas of drainage (very roughly overlapping with historical territories of Bohemia, Moravia and Silesia):
Almost 2/3 of the country is drained in NW direction through the Elbe into the North Sea.
The Morava flowing towards SE collects water from eastern regions of the Czech Republic and discharges into Danube which flows to the Black Sea.
The northeast and some northern portions of the territory is drained by the Oder and its tributaries like Lausitzer Neisse into the Baltic Sea. The corresponding watershed tripoint with a marker for symbolic "roof of Europe" (50°9'27"N 16°47'27"E) is located at Czech-Polish border on Mt. Klepáč near Dolní Morava in Králický Sněžník Mountains.
The catchment area of the Elbe down to Czech-German border in Hřensko/Schöna covers 51,394 square kilometres (19,843 sq mi). This figure includes upper courses of some tributaries starting in neighbouring countries. The area solely within Czech borders is slightly smaller and this is the figure given in the following table, which shows Czech territory divided after drainage basins.
Table of rivers
While the Elbe is the longest Czech-related river when measured through its overall length (i.e. including its lower course in Germany), its tributary the Vltava surpasses it as the longest river within the territory of the Czech Republic itself. (In fact the Vltava also carries more water than the Elbe at their confluence.)
Hierarchical list
Rivers not located themselves within the Czech Republic but possessing tributaries originating on the Czech territory are shown in strikethroughitalics. Rivers over 100 km long or having average discharge greater than 10 m³/s are emphasized in bold.
Rivers flowing to the North Sea (Elbe basin)
tributaries joining the Elbe during its course through Germany (from area along Czech-German border in NW of the country, esp. from the Ore Mountains)
Elbe; leaves the Czech Republic at Hřensko, empties into the North Sea)
tributaries joining the Oder during its course through Poland (from northern parts of Bohemia (esp. around city of Liberec - Frýdlant Hills, Zittau Basin and NW slopes of the Jizera Mountains) and NW portion of Czech Silesia (esp. Jeseník District))
Oder (leaves the Czech Republic at Bohumín, empties into the Baltic Sea)
rivers from SE regions of the country (i.e. most of Moravia)
(The Morava accounts for almost all discharge, the only exception being the Vlára, which belongs to the Váh subbasin)
Danube (empties into the Black Sea, does not itself reach the Czech territory (flowing only through neighbouring countries of Germany, Austria and Slovakia)
Loučka (originates through confluence of Bobrůvka and Libochůvka)
Bobrůvka
Libochůvka
Jihlava (in fact a tributary to Svratka but nowadays their confluence is completely within Nové Mlýny Reservoir, thus creating an impression of a direct tributary to Thaya)