The map shows the altitude of water table surface above seal level in the glacial deposits that form Block Island. Because the sediments are only moderately permeable, the water table is close to the to the surface in most parts of the island, even in hilly areas. The map represents a generalized water-table configuration on the basis of data from many different sampling periods; because the data were collected at different times, they should not be used to determine a specific depth to water at a particular site. Water levels measured in 117 shallow wells (less than 35 feet deep) from June through September 1962 and from March through September 1988-90--periods when water levels were at about the same altitude above sea level--ranged from less than 1 to 24 feet below land surface and averaged about 6 feet below land surface.
Additional publication details
USGS Numbered Series
Generalized water-table map of Block Island, Rhode Island
1 map ;90 x 63 cm., folded in envelope 30 x 24 cm.