A.C.
If you are already exercising regularly and watching your diet...you probably don't have 10 lbs. of water weight hanging around.
If you are retaining water because of your menstrual cycle or some other reason, there are certainly some dietary things you can do to diminish the effects:
moderate amounts of caffeine coupled with drinking lots of water
avoid carbonation
asparagus
all types of melon
artichokes
parsley
dandelion root