Roughly around 3.20 billion gallons a day
Glaciers shaped the landscape is the answer. Actually, in Nova Scotia near Halifax there is a glacial boulder or erratic of basalt which is deemed to come from about 130km away perhaps from the north or NW. Also, there are glacial striations there on the bedrock which can be used to determine the sense of the direction of flow of the ice. In New England, there are pro-glacial lakes. Both the Maritimes and New England were most likely covered by the Laurentide continental glaciation.
