This is a word blend of “depleted” (to use up or empty out) and “replenish” (to fill up). Since REplenish means to fill again, then it is reasonable to assume DEplenish would mean the opposite. I heard this one on the Pittsburgh CW 10:00 news, in a discussion of salt supplies in Cleveland. Although malaphors are generally mixed phrases or idioms, they can appear as mixed words or word blends as well. See my other word blends in the category list under Word Blends.