Bend Tarp Liner makes liners that are much more lightweight than the EDPM liners.
https://www.btlliners.com/Look at their AquaArmor line of pond liners. It's a fabric, so it's relatively thin and lightweight, but it's water tight and it's VERY tough. You can call them and get a small sample sent to you.
From reading the start of the thread to now it seems that you have a high water table in that area, and you dug the pond to have a place for the water to go. So, that precludes using a liner or sealing the pond, because when you do that then the water that is in the ground can't migrate to the pond.
If you line the pond, then you have to have a source of above ground water to fill the pond. Either runoff or a well/pump.
The stump has to come out of the pond if you want to keep and seal the pond.
If you want to keep the pond, then you will have to put in a liner or use SoilFLock or a similar product to seal it because the water in the pond is just the water level in the ground. There is really no "spring". The water level in the ground will bounce up and down according to how much rain/snowmelt you get.
In any case I'd dig a cistern in the front yard. It could be a tube stuck down in the ground with holes in it to allow water to get into the tube. You will have to use a filter material on the outside so it doesn't fill with soil. Put a hard top on it so nobody falls in or twists an ankle.
Have a pump in the ground attached to a float, like a sump pump. Have it attached to a "T" with one side going to the pond, another side going to the curb. Bore thru the curb to the gutter in the street, install that cistern, plumb it to the pond and to the hole in the curb. With the pond being lined, pump water into the pond from the cistern to keep the pond full, but during high water table times, pump the cistern dry and shove it to the curb. That way your yard will stay dry.
