IIRC, there's no way to know if a spring will still have positive pressure once you have all the pond water above it at the desired depth.

So, any given spring might go both ways, in or out.

Of course, some situations exist where the outlet of the spring is high enough, or higher than your desired level. Or, the spring has enough pressure to stay positive and keep your pond full, although i think this is more the exception.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."