Invisible Edge - Plumbing ?

I want to create an invisible edge on a new pond.
I've worked out the flow rate over the edge etc & the pump size etc.
And I've had a few ideas re the plumbing.
Basically I'm thinking of a storage tank idea, but if I
go on holiday & the pond level drops a little then I'm concerned
about the storage tank emptying, and the pump running dry.
So I started to think about 1-way valves etc etc to refill the tank but
it all got complicated.

Anyone done an invisible edge pond or pool? how did you setup the plumbing?