[2][3] Entirely in the department of Loire-Atlantique, the Acheneau crosses the nine municipalities of Saint-Philbert-de-Grand-Lieu (origin), Bouaye, Saint-Mars-de-Coutais, Saint-Léger-les-Vignes, Port-Saint-Père, Brains, Rouans, Cheix-en-Retz, and Le Pellerin (confluence).

Its origin lies in the zone "Boulogne from the Rau du Redour to the Lac de Grand Lieu & the Acheneau from its source to the Tenu".

When considered with its tributaries (Blanche and Tenu) and the rivers of the Lac de Grand Lieu (Ognon and Boulogne), the entire watershed covers a vast swathe from the south to the west of Nantes.

[1] L'Acheneau is managed by the Syndicat d’Aménagement Hydraulique du Sud-Loire (South-Loire Hydraulic Development Syndicate) (SAH).

To manage water levels in the bordering marshlands, the Lac de Grand-Lieu, the Tenu, and even as far as the Marais Breton, a complex system of automated and remotely controlled locks, sluices and pumps have been developed on the river and related watercourses to regulate the flows.