Evaporation/splashing or liner leak

I have an AG 4'X18' round pool. It seems like everyday I go out and it looks like it's lost some water. The kids have been very active in it this year splashing around also we haven't had rain in a while. The past few days have been sunny in the high 80's pool doesn't get any shade at all.

My question: is there a test to see if it's just evaporation/splash out or a leak? The last time I filled the pool was about a month ago. Very little rain since then and the pool level has dropped about 1 1/2"-2".

If you can keep the kids out for a few days... Place a 5 gallon bucket on a step and fill with water to the same level as the pool ( I place a big rock in the bucket to keep it from floating) .. let sit for about 3 days. If the levels are the same you can rule out a leak. both will evaporate at the same rate.

being back east this may not be true but out here in Az with 110* temps and 7% humidity, I have to add water every couple days .