You can try a cover up more of the top, but you are going to have humidity issues with a heat lamp. (Do you need the lamp to keep your temps up? 82 cool side 92 warm side) I'd move the water bowl over the heating pad, as it will help the water evaporate a little faster. You may also want to consider putting a humid hide into the tank as well.

The only other thing I can think of is adding a humidifier to the room. Good luck.