Sacha writes
My problem will be that there is no electricity in that area and no
naturally running water so I think it will just end up as a stagnant
puddle, which seems a bit self-defeating.

You may be OK. For various reasons we are not running the pumps in the
front garden atm (haven't for at least a couple of years) but the ponds
don't seem to be suffering. One has a bit of sun, and the frogs breed in
that one (the newts have now found it too). The other gets sun only from
the NW or NE, and the frogs move to that to escape the heat of the
summer. The third is much tinier, with no amphibians, but still has good
insect life and is relatively sweet. Water in all three is clear. I
think if you can get the balance right, with sufficient depth of water
and good plant growth, you can keep it going without a pump.
--
Kay