I believe it's intended to funnel cool air through the grille and up to your intake, it's not sealed to your intake box so I'm guessing gravity keeps it from sucking in water, with a snorkel you are already getting cooler ambient air which is the function of this duct, the snorkel you're looking probably flows much less air than the factory system, but I don't think removing that duct will have an impact specifically since a snorkel won't be pulling air from the factory location.