Do you have any flowing creeks nearby on the land that you can harness some energy from? i.e. a turbine?

Otherwise solar may not suit if there is nobody there to get snow off of the panels. A combo of solar and wind may suit.

The greater depth may go a long ways to stop winter kill based on the larger capacity of O2 in the pond. Aeration will of course help even more. Note the springs wont add much to the O2, if not take away unless you splash them over some rocks to oxygenate the water a bit.