The rivers of Catalonia can be classified into four groups according to their source.
The Llobregat deserves a special mention because of its importance: its basin covers most of the province of Barcelona. It source is in the Pyrenean Serra del Cadí in the municipality of Castellar de n'Hug (Berguedà) and its valley is one of the main north–south communication routes in Catalonia.
The Aran Valley is the upper valley of the Garonne (la GaronainCatalan, era GaronainAranese), an Atlantic river which meets the sea near Bordeaux, France. The boundaries of the comarca do not correspond exactly with the watershed, and both the Noguera Ribagorçana and the Noguera Pallaresa have their sources on its territory.
The frontier between Catalonia and the Valencian Community is formed for much of its length by the Sénia, while the Noguera Ribagorçana forms the frontier with Aragon for much of its northern half.
Rivers are listed according to their estuaries, from north to south along the Catalan coastline, or according to the point of confluence, from the sea to the source, for rivers which do not flow directly into the sea. Names are given in Catalan with the appropriate definite article: Spanish names are given in parentheses. Catalan names are usually preferred in English language works, except for the Ebre which is usually referred to by its Spanish name Ebro.
The Catalan language has two words for "river", riu and riera. The word riera is used for smaller rivers and for streams, and often indicates a seasonal river. Of the above list, only the Gavarresa is commonly classified as a riera, all the others being qualified as rius. The grammatical gender of Anoia is feminine, while that of Ebre is masculine.
The main economic importance of the Catalan rivers is probably the role of their valleys as communication routes, particularly through the Coastal and Prelitteral Ranges. Hence routes inland from Barcelona pass either through the valley of the Llobregat or that of the Besòs, and the Francolí valley is an important route inland from Tarragona.
Irrigation is important in the drier areas of Catalonia, notably in the Central Depression and in the south. The Canal de Aragó i Catalunya and the Canal d'Urgell distribute the waters of the Segre across the comarquesofNoguera and Segrià where it is used for growing cereals, almonds and olives. Irrigation is also important in the comarquesofBaix Ebre and Montsià, where the cultivation of rice is widespread.
All of the larger Catalan rivers, with the exception of the Llobregat, have been dammed for hydroelectric power. By far the largest dams are those on the EbreatRiba-roja and at Flix (Ribera d'Ebre). Other dams include
