Depo Provera generally does not affect vaginal lubrication but for some women, this might be a side effect. There are water soluble vaginal lubricants that can be purchased (over the counter, without a prescription) that will help with dryness, for example: Astro Glide or KY Jelly.
Vaginal dryness is NOT permanent and once you are off of a hormonal method of birth control (that includes birth control pills, patches, and vaginal rings, as well as Depo Provera), your normal vaginal mucus will return – but your ability to get pregnant will also return!
Never use an oil-based product, such as Vaseline (petroleum jelly) because they can actually hurt vaginal tissue and cannot be used with condoms. Additionally, you should avoid products that contain oils or fragrances because they actually can cause vaginal irritation and increase the chances of getting a vaginal infection, like a yeast infection. Douching is NOT effective for moisturizing and will also increase the risk of infection.