Here is a very simple solution to a dry pond caused by a plumbing break.
If you are drawing water direct from your bottom drains.
Connect one side of a length of 8 to 10mm tube from anywhere on the suction side of your pump. Place the other end at a depth in your pond that you are sure your fish will survive in for as long as possible, I suggest about 40% down so you will be left with 60% of your pond water. This tube will ensure that the pump suck in air when the water level reaches that point. This will keep the water level at that point should there be a burst in the pipe or a leak somewhere in the pressurised side of the plumbing. You can hang a weight on the tube to keep it there. If you have an air stone running the fish will survive for a few days.
f you are drawing water where the pipes to the pump were installed over the edge of your pond then a 6mm hole should be drilled in the suction line again at that level that you regard the safe water level should something go wrong.
If you are drawing water from a sediment chamber do the same unless your sediment chamber is designed in such a way that it won't empty your pond like in the following drawing:
By: Chris Neaves