Well, the power usually goes out cause its raining heavy

, so it might stay wet, however, Im wondering about the media dieing from lack of O2. I would think that if the power was out for days (never happens here), the submerged would be better because some bacteria would have to live, but complete drying out, should kill everything.
JG12: Im not talking about something that large scale. A pump that draws from a skimmer doesnt have that large of reserve. Typically the skimmer is the lowest point in the pond, and as water evaporates its level gets even lower. Like a Savio, Could only hold 30 gallons.
Im talking about a 4' long by 2' wide chamber about 4' deep. Then below that a small resevoir pit for the pump to draw water from, enough that it doesnt suck air. The auto-flill for the pond would be down in that pit. The pit should be high enough sidewalls, so that if the power went out, it would not overflow all the pond water out of the system. Something of this size is very easy to hide under a deck or walkway.
I realize this is not ideal and that a raised BH is eaiser, Im just daydreaming the idea. Its my non-conventional nature.