The Northern Alps, specifically the Haute Savoie and the high Val d’Aoste, have many rivers. The Arve in Passy, the Giffre in Samoens, the Dranse in Thonon and the Dora Baltea in Courmayeur. They are very different, both in terms of their characteristics and their source of water (glaciers, melting snow, rain etc.).
The Arve and the Dora Baltea are 2 rivers fed by the mighty glaciers of Mont Blanc which swell their waters in June, July and August.
The Dranse and the Giffre are fed by snow and rain. Their maximum volume will be in May and June, gradually diminishing but still maintaining a good flow.