Do you have a pump running? via a small stream or external filter?
here in the West Midlands we have rare nights where one of our ponds has not
frozen over, Have 3 small ponds wildlife only only and one with fish which
has pump running into header pool then a small stream back into pond, the
pumped pond does drop water level but the header pool can form a sheet of
ice and over flow, the other ponds can freeze over and water level does drop
afterwards I guess with evaporation.
Any drop of water which you consider serious , leave until water fails to
drop anymore then check at water level for leakage.
Best advice I can give.

"Broadback" wrote in message
...
Since the cold weather freezing the water my pond level has dropped
substantially. Is that likely to be natural or has it developed a leak?
--
Skulking in the low lands of North Staffordshire
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