Ground water

Stratified drift, deposited by water flowing from melting glaciers, forms the most important aquifers in the Charles River basin. Fifteen moderate- to high-yield stratified-drift aquifers have been identified in the basin above Waltham. These aquifers occur along the present river and tributary channels and are connected hydraulically to the Charles River. They cover about 75 mi2 or about 30 percent of the basin above Waltham, and range in area from about 0.3 to 10 mi2.

The saturated thickness of the drift deposits generally increases from southwest to northeast across the upper basin. Town wells in drift deposits with an average saturated thickness of 50 ft yield from 100 to 1,500 gal/min, and average about 500 gal/min.

Most bedrock in the basin can provide a few gallons per minute of water to wells for domestic, farm, and minor industrial needs. Yields reported for such wells are usually between 1 and 5 gal/min, but may be as high as 50 gal/min.