There is a story that I have read of an early Greek philosopher, probably Thales. The man was also merchant, and during one of his trading journeys a mule happened to slip and fall while crossing a stream. The mule was loaded mostly with salt, some of which dissolved and washed away. The mule, having noticed the lightened burden, made sure to fall into the next stream also. The philosopher put a quick end to this by loading the mule with sponges for the next trip.
I don't suppose that mulch absorbs water to the extent that sponges do, but then none of the sponges I have dealt with have been measured in cubic feet. Today I fetched four bags of mulch back from the garden center, and was disappointed to hear that I should stack them back by the fence for fall use; they'd be sure to soak up water in that time, and be heavier to haul. As it turned out, a couple of the bags had already got their soaking, and are unlikely to be worse.