Ladybower dam.. from a distance... and No. '33'

Seen during a walk along 'Stanage edge' are numerous of these man made grooves and bowls cut into the rocks...here is number '33'....but what are they ?

After doing some looking around on the 'Net'... I discovered that they are provided as a source of drinking water for the 'Grouse' ... this is when the land was privately owned .. around 100 years ago and supplied for the poor Grouse which were specifically reared to be shot.. by the wealthy land owners and their pals !