The valley is part of the hydrographic basin of the Dora Baltea, and has a U-Shape. Just before Cogne, it divides into several minor valleys: the Valnontey, leading to the Gran Paradiso, the Grauson Valley, with the eponymous peak, and, eastwards, the Urtier Valley and the Valleille. Al these valley are crossed by stream. which flow into the Grand Eyvia, which in turn flows into the Dora Baltea before Aymavilles.