Lynne, IMHO...
I would STRONGLY suggest you heavily weigh the percieved benefits vs. the potential risk. To me, this is just a leak or hazard waiting to happen.
Enjoyment level ~5?
Potential problems ~10?
Punch your own numbers in...
Settling Earth, seals, plus many, many more possible reasons could result in a complete disaster.
Have you considered a stream between both ponds? (Visible, less pressure, less chance of leakage). And you could check out the action in between...
Mitch
My Opinion - Worth What You Paid For It...