Do you really need "respectively"? It doesn't say anything that isn't already said; it's superfluous; the order is already mentioned. Delete it. Use "respectively" when it truly matters:

The corresponding sewer projections for the monthly and yearly flows are 18 and 200; they were 15 and 139, respectively, under previous projections.

It's really pointless to speak of gerunds and participles; the distinction just doesn't hold up to close syntactic scrutiny, which is why some just call them the "ing" form of a given verb. When the "ing" form takes the syntactic place usually occupied by a noun, the "ing" form takes the possessive as its subject. That is standard English. Whether the "ing" is or functions like a noun is irrelevant. Informal English (particularly spoken English) often uses the objective form of the pronoun ("me," in this case) as the subject of the "ing" word. That is non-standard English (or "incorrect" if "me driving proves that I am a fast driver" occurs in some formal context).