I don't know of a way to pump water from a well to a pond in enough quantity that will also leave enough water pressure in the house for daily usage.

As for length of time, I've run my well for months straight into the pond @ 25 gpm.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).