Question
My pond loosing water as much as one inch per day (pond size 7ftx7fx3ft ) .  Water lost from the waterfall, not from the pond .  Is this normal ?  How to stop it ?
Thanks

Answer
Did you check for any leaks on the waterfall?
Do you leave the waterfall constantly on?
The longer you leave it on, the more water you would lose trough evaporation.

You can do a simple test:
Leave the waterfall runing all night long.
Check how much warter was lost.
Then, leave it running all day long.
If you are losing the same amount of water on both times,
maybe you have a leak somewhere.
Otherwise, you should be losing more water during the day, when it is warmer and the water would evaporate faster
Good Luck!

Carlo