I have been trying to find the leak in my 1 acre pond for about 2 years now. This year I have started getting really serious. I am determined to find it. My strategy is to drain the pond little by little till the level stabilizes. It was leaking 1/4 inch per day half full during cool weather. As the level dropped, I walk the bank looking for soft spots. Found some sand in one area but looks to have good clay under it. I'm about to rule it out as my problem plus the water level still dropped the same amount after I drained it a good 2 vertical get away from the area. Just today I noticed the face of the dam seemed really towards the middle. Using my shovel, I dug holes about 1 ft deep 1 ft from the edge of the water. Did this along a large area of the dam. I noticed in many cases, my holes filled with water instantly at the same level as the pond. Some only filled a little and others didn't leak at all. I don't see water behind the dam at all. If it's leaking into my dam then the water must find a path down is all I can think. But I don't know what's normal for a dam. Since it's constructed, do all dams leak water into their face to some degree? I attached pics to show what I'm talking about. I show the area where I dug and an example of the seepage plus a shot where no water leaked back. What are my options here? I have soilfloc ready to use from last year. I never used it because I wanted to target my problem zones for best results. Do you all think the dam is the most likely source of my leak?

1/4 inch a day....evaporation?

I'd like to add that I cut a bunch of cottonwood trees of my dam last year. This pond was neglected for years and then enlarged during the drought a few years ago. Ever since then, it's had trouble holding water. This time last year it leaked 1/2 inches per day. After the record rain we received last year, the leak has slowed to 1/4 inches per day so that is promising.

I didn't think evaporation comes into play with cool weather.

Evaporation depends on the water surface temperature and dew point. During the drought this winter, we have sometimes had pond surface temp in the high 50's with dew points in the high 20s to low 30's, along with strong winds. That leads to considerable evaporation.

You probably do have some small leakage in addition to evaporation. If I could get my leakage down to 1/4 inch a day when the pond is high, I would be happy. Mine's about 5/8 inch a day when the water level is high. After about 30 inches of decreasing per day loss, the water loss is about 1/8 inch per day.

I tried Soilfloc last year in the areas I thought my leaks were, and they slowed a little but the losses resumed after a few weeks.

I think my water loss is higher when the pond is full. I never tracked it because I knew the leak was much lower. Also in the heat of the summer, I didn't know how much loss was attributed to evaluation.

I have a pallet of soilfloc but I want to use it as a last line of defence.

Ice and snow can evaporate without melting when conditions are right

Ok I will agree there may be some evaporation but while my pond drops, others in the area remain stable. They might have lost 4 inches all winter. Mine loses that in a week.

Water leaking back into the dam from the shore line is a problem right? I don't know how far the water back the water goes but I did make a couple holes behind the leaky ones and the soil was not nearly as wet.

Leaks are a never ending loss of sleep for me. I lose 1/4" a day, pretty much year round. I know I am losing some to a leak, but with a leak that slow, there's no way to add dye to the pond and track it. I tried the soil floc, I think it slowed the leak down somewhat.
If I could get 3" of rain a month, I'd be fine, but when you have the draught we've had here for so long, it's just frustrating to watch the pond continue to drop. Last significant rain was last August.
I hope it slows down some, with muck forming on the bottom of the pond. Who knows. I do compare my pond with others in the area. Mine is almost always the lowest. That's the only unscientific proof I have, that I've got a leak, in addition to evaporation.

I think my course of action is to treat the soil with bentonite and soilfloc. Then go over the top with soilfloc when the pond fills back up. Just have to figure how much bentonite I'll need to cover roughly 500 sq ft. I can get 100 lb bags for $20. How many would I need?

In my experience, you need about 50% more Bentonite than Soilfloc. Throw the Bentonite on top of the Soilflic to promote sinking. I don't know if it really helps. I think Soilfloc works best if your pond is muddy with clay. Mine is fairly clear, so effectiveness likely diminished.
My pond is not difficult to keep nearly full with pumping when we have normal rainfall. We haven't had normal rainfall for over seven months.

I'm mixing bentonite and soilfoc into the soil. Then I will apply soilfloc when the pond rises with rain... Hopefully. I'm not sprinkling bentonite in the water.

I suggest you call Mike Otto for his advice. There are different ways of applying additives (Bentonite and Soilfloc). Different people and methods have provided widely differing results.

I need some more advise for sure. I'm also wondering what a jumping jack style compactor will do for me. I need to pack the dam face in that area when it dries out a little.

Now I'm wondering how a guy can pack the dam face on a 30ish degree slope. Could a backhoe or excavator reach down and pack with the bucket? I can smash my boot in the soil but there has to be a better way... I wanted to try a jumping jack but I think it would end up in the water.

They make packing rollers for trackhoes, but the availability or cost for your area could be an issue. It is basically a heavy roller that goes where the bucket goes then the operator puts additional down pressure with the boom.