The Bastan river, known locally as the Gave de Bastan, is a right tributary of the Gave de Gavarnie and has its source in the north-east of the commune near the Col du Tourmalet whose slopes and the slopes of the surrounding peaks supply water. The Ruisseau d'Aygues Cluses rises in the south-east of the commune and flows north to join the Bastan. The Ruisseau de la Glère flows north from the Lac de la Glère in the south-west of the commune to join the Bastan east of the village. Two small streams rise south of the village and flow north to join the Bastan: the Ruisseau de Rioulet and the Ruisseau du Pontis.