Jeff_G,
First off...Welcome to the forum...It sounds like you have a really neat pond!
It does indeed sound like your pond is spring fed. If there is no inflow, the water has to be coming from the pond basin. Does the pond have any outflow when it hasn't rained recently?
If no outflow is seen, the pool height can't be rasied because the spring will act as a drain if the water level is raised above it's maximum.
As for your clay problems. I suggest you read the thread titled Alum kicks Clay Butt in the Muddy Water section...there is a wealth of information amongst the hyjacks and humor.
In your area, you may need a combined approach to clear the water long term...First get a soil sample test from both inside the pond basin and surrounding soils to see if iit needs Lime...it probably does. You may also want to add a couple tons of Gypsum follwed after that with an Alum treatment.
