Pond leaking

Ok so please see picture.  its ridiculous and i laughed drawing it in all of 2 minutes. I Have a pond directly to the left of my drive.  Between the drive and the pond is grass and it stay extremely wet (soaked) and the ground stays like that at the lowest point up my drive for about 30 more yards.  The wet side of the pond isn't level with the ground, its damned up many feet.  

The pond is spring fed.  I just bought the place and the old man told me he thought it was muskrats that was causing the leak.  I checked the pond and see no slicks or activity/holes that indicate muskrats exist.  The pond had repairs done many many years ago to stop the leak (so its been around a while) but after 2 years it started leaking again in the same way.  The pond does have many trees around it but non of them are more than a foot in diameter so i would think the roots would be causing an issue.  What options do you think I have to get this fixed?  I was thinking of using bentonite clay or using dye to see if even reaches the area that's staying wet.  One thing i have noticed is that that water level doesn't increase in the wet area, but it also doesn't recede.  Its just status quo year round it seems.

Are you actually loosing water from the pond?
How high is the bank?
Roots from those trees if growing on the bank which is holding the water back would be the first place if would look.
They normally are a cause of leaks when old roots die and rot.
Bentonite is a god product and pond liners are also very good.
What are your plans for the stored water?

The water is just for fish and what not.  I'll post pics shortly.  Thanks man

Tried to get a couple pics before dark.