Is north the top of this pic? Never knew there are 3 dams.
yes noth dam on top - to the left is the earth dam (dike?)
There is a separator for the swim area by the boat ramp(not pictured) - i'm not sure what that is called, it isn't a weir.
and the south dam, straight line structure at 9:00 in the picture.
At the south dam is the pump station to feed water into the res (it is not naturally fed)
it is the left side of the dam, to bring water in from the south branch of the raritan - a couple miles west of there.
It looks somewhat excavated - but i might be imagining it.