I've noticed a higher than normal evaporation rate in my pool this year as well. Just chalk it up to hot dry air in Aridzona.

To check to see if it's a leak or evap, set a 5 gallon bucket on your steps and fill it to the same level as the pool. let sit for a day or so. If the water in the bucket drops at the same rate as the pool, it's evap. If not , you have a leak.