ok... let me ask you this... the water level of the second pond will be lower than the water level of the first pond... but will be higher than where the water is coming out of the first pond...
As long as the water level of your second pond is below that of your first, the first (main) pond will continue to leak. The leaks that are submerged by the second pond should slow as the head (water level) of the second pond increases but it won't stop completely until the levels are equal.
The pumping idea seems like it would increase the average level of your main pond but in addition to the initial cost, you'll have operating expenses from that pump. Very rough estimation... $550 - $600 a year just for the juice to run it 24/7.
I have essentially zero practical experience but if it were me, I'd look more closely at those "streams" and see if I could figure out what's going on. Every gallon of water that flows through there will take a tiny piece of your dam with it. A second pond will be wasted money if your dam falls apart in ten years.
