Hopefully somehow out there is better with math than I.
Suppose a giant ball of ice, 130km in diameter (water volume significantly greater than the Great Lakes) were to strike the moon at a speed of 3km/s (just above the moon's escape velocity). If my math is right, most of the water will remain on the moon in the newly formed crater, though I'm sure a significant amount would sublimate away over time.
Any help would be appreciated.
Oh, and this is for a possible scifi story. I just want to make sure the basis for the drama is at least plausible, it doesn't have to be 100% exact.
The question, how much water would end up left behind? I'm not sure if it would rival Lake Superior, Lake Erie, some other lake, or essentially none at all.