WATER

Most of the Earth is covered in water.
The water in oceans, the sea, rivers and lakes is surface water.
The water underground in rocks and caves is groundwater.

Imágenes del Lago (Abreu, Delgado y Boileau) y del Río Duero (Fernando Cristobal Pintado)
ambas  del Bancp de Imágenes y Sonidos del ITE.