Hydrogeology and Processes of Acid Neutralization in Cadwell Creek Watershed, Quabbin Reservation, Massachusetts

摘要

A detailed hydrogeological and geochemical study was undertaken of Cadwell Creek, a small (7.28 sq km) forested watershed on the west side of Quabbin Reservoir in central Massachusetts. Paleozoic crystalline metamorphic rocks comprise the bedrock in the watershed and are the source material for the glacial till, the main aquifer. During 1983 41% of incoming precipitation was returned to the atmosphere as evapotranspiration and 55% left the watershed as stream runoff. Furthermore, 45% of this stream runoff was groundwater discharge or base flow. Specific conductivity and pH, both field and aerated, showed strong correlations with the groundwater velocity and hydraulic gradient. The pH ranged from 4.7 to 7.0 and the specific conductivity from 25 to 70 micromhos/cm. Two-thirds of the total base flow comes from areas with low pH and low specific conductivity, i.e., is incompletely neutralized. Because of unusual hydrologic and topographic relationships, Cadwell Creek alone should not be used as a standard for all streams draining into Quabbin Reservoir.