I attempted a repair on my pond and up until a week ago, it has only been 1/4 full and barely over the patch due to lack of hard rain. Now it’s up about 90% full and time to test water loss. Temps have been in the mid 90s with wind past few days and my pond dropped 1/2 inch per day. It used to drop an inch at full pool till reaching half pool where it slowed to 1/2 inch. Seems I slowed it down but I’m not sure. Has anybody tracked their summer water loss vs winter? Really interested to hear from guys that drop nearly zero in the winter.

1/2 inch drop per day of hot, dry weather seems fairly normal in a pond which does not have a source of constant water inflow.

I'd say 1/2"/day thru evaporation is about right for my pond as well.

Now that we're out of our summer drought, I've considered drawing my pond down a foot or so when temps drop enough to make room for fresh water thru the winter and spring. It doesn't take much for my pond to fill back up.

I will lose between a qtr to a half inch per day. I don't think it is all due to just evaporation since most ponds experience some seepage. I think I lost more when I ran the diffusers 24/7. Now I just run them at night. That helped reduce my water loss.

Set a bucket of water out by your pond check how much loss is in the bucket. I have found this to work well to gauge evaporation loss. The bucket can get warmer and loose a bit more then the pond some days.

If you search for evaporation and precipation for your state you will likely find a website with relevant data. The average amount will depend on your location and in some states the data is quite detailed.

The monthly data varies from year to year but in general the evaporation and precipitation are inversely correlated, that is, in months where the precipitation is above normal .... the evaporation will be below normal.