What does the latin expression "Aquae pluviae arcendae" mean exactly?

Under the Latin expression "Aquae pluviae arcendae" is called that legal action for the defense of damages against property, produced by the neighborhood that claims through its exercise, the prohibition of altering with works the flow of waters to the detriment of the other farms/plots, also called "actio aquae pluviae arcendae".

The lower estates are subject to receiving the waters that, naturally and without the work of man, descend from the upper estates, as well as the earth or stone that they drag along their course.

In this sense, the Spanish Civil Code (CC) establishes that the owner of a property in which there are "defensive" works to contain the water, or that due to the variation of its course it is necessary to build them again, is obliged, at her/his choice, to make the repairs or necessary constructions or to tolerate that, without prejudice, they are made by the owners of the properties that experience or are manifestly exposed to experience damage (arts. 420 and 552 CC).