I have a GE Profile dishwasher that has an airgap that fits through my countertop and allows overflow to drain into my sink.

I am moving and re-installing the dishwasher but my new granite countertop with undermount sink does not have an extra hole for dishwasher airgap.

Do I need airgap? Must I have a new hole drilled in the granite? Is there another way to do this?

Thank you for any help.

No, you can install your dishwasher using a high loop. Some areas require an air gap, some do not. Some plumbers prefer the high loop method over the air gap.