How do I locate the "leak" behind my stone cascade?

[lachancesare]

I am now enjoying the third season of our double level pond with stone cascade but a problem has popped up I need advice on addressing. I am noticing I lose about 2" of water a day and am pretty sure it is escaping from behind my mortared stone cascade. I checked the top for any likely spots and did a couple of minor repairs which slowed down the leak but did not stop it.
I see that some stones at a far end of the upper pond are "oozing" a trickle of water (about 4 feet from the cascade itself). while the hose that feeds the upper falls is directly above this leak, I checked the hose and it is tight and dry.
I assume water has somehow gotten under the double layer of liner I put under the cascade when it was installed. I suspect a critter may have chewed through the liners and the water is finding its way to where the "oozing" water is....
My problem is that this is a steep hill and the affected area is right under a rather large evergreen bush....the area I'll have to dig to find the leak will be hard to reach and is planted in established perennials.
Any suggestions as to how I might do this in the least harmful way?....I have extra liner I can use to patch the bite/rip if that is what it is but I sure don't look forward to having to de-construct the cascade itself if I can avoid it.
I will post a couple of pics to show the effected areas.

 

[tbendl]

I would try maybe doing more extensive repair where you found the original leak. If you can completely divert the water away from that area and see if it continues leaking then move on, but I'd go with where you had a leak.

 

[Meyer Jordan]

If the leak is indeed behind your waterfall cascade, demo may be the only option.

 

[Tula]

We have a stone mortared waterfall and had a leak a few years ago. We took it apart, used some of that canned "foam" that hardens, then dry stacked it back into place.

 

[addy1]

I stopped a leak I had in a water fall I just did not want to rebuild. Looked until I found the likely water escape point and used some of the pl roofing repair stuff, put a layer of it under the rock to divert any water back down the main fall. It worked great and is still holding 4 years later.

 

[mgmine]

Turn off your water for a day and make sure that it isn't coming from some other place.