I am sorry your are experiencing dry eyes after your blepharoplasty. Patients that have dry eyes before a blepharoplasty are a risk to developing drier eyes after surgery. If a patient has dry eyes before a blepharoplasty, I send them for special tests to ensure they are able to make enough tears. If they can make enough tears then they are not a candidate for surgery.
In your situation, it is hard to tell you what is going on without a picture. If the surgery changed the position of your lower lid to a point to where it is not in good contact with your eye, it can cause your symptoms. There are a variety of other causes that can cause your issue, and you need to see a qualified eye specialist to ensure you eye is in good health.
I hope this helps.