Aa is the name of a large number of small European rivers.
The word is derived from the Old German aha, cognate to the Latin aqua, water (cf. German -ach). In German also Au and Aue exists with the same meaning, similar to å in North Germanic languages.
The following are the more important streams of this name:
two rivers in Latvia, Lielupe (in German Kurländische Aa) and Gauja (in German Livländische Aa), both falling into the Gulf of Riga, near Riga, which is situated between them
a river in the north of France, falling into the sea below Gravelines, and navigable as far as Saint-Omer
a river of Switzerland, in German Aabach, in the cantons of Lucerne and Aargau, which carries the waters of Lakes Baldegg and Hallwil into the Aar.
in Germany there are the Westphalian Aa, rising in the Teutoburg Forest, and joining the Werre at Herford, the Münster Aa, a tributary of the Ems, and others.
in the Netherlands, a river in Groningen province that flows through Groningen city.
