jmsbert
Thank you for the note.
The water reservoir you are referring to had been mapped based on Grafcan imagery some weeks ago. Grafcan imagery is one of the main sources to add buildings, highways as it is mostly of high quality and orthographically taken. In this case the basin must have been abandoned in the last years which was not visible on the imagery that was used by the mapper. After checking against the drone imagery offered by https://www.opendatalapalma.es the object has been removed by a mapper. 

The greenhouses and landuses (orchards) mapped on 2021-10-14  (e.g. way 992908150) seem to fit well to the drone imagery. Therefore I will close this note.