Artificial lake for power plant?

The artificial lake used for water storage for hydroelectric power plants, besides the tagging with natural=water + water=reservoir,
as the plant cannot work without it,
shoud be considered part of the power plant?
if yes, is there any recommended additional tagging or relationship to model that it is part of the power plant?

I understand that tags for the lake are optional, as it’s said at (picture below):

So it could (not mandatory) be considered part of the power plant (being the plant an area, or relation type=site).
If it’s opted to include it in a relation:
-power plant: type=site… +etc … (like )
-lake: role=water-storage (like )

Thanks, role water-storage was what i’m looking for.