Some of these water courses are permanent, such the Este River, which feeds into the Ave River. The Esteiro River's source is at the base of Mount Cividade and it empties at the beach of Aver-o-Mar while the Alto River's source is at the base of Mount São Félix and it reaches the Atlantic at Rio Alto Beach. The land is well irrigated, the appearance of springs and wells are very common, given that, often, underground water is close to the surface.