The other consideration to take into account is O2. At that depth, it is highly likely that the water you are pumping out has very little (most likely right around 0) oxygen, so you will want to oxygenate it before it gets to the pond if you already have fish. This can be really easily done by agitation or mixing, you essentially just don't want to run the hose down and pump it in under the surface of the pond. It will oxygenate quickly if you expose it to air first. When I added to mine with a hose last year during the drought, I just sprayed it against some rocks before it flowed down into the pond and didn't have any issues.
