Water quality in the Cambridge, Massachusetts, drinking-water source area, 2005-8

Abstract

and in published reports (for example, Smith, 2005). From 2004 through 2008, the USGS and CWD characterized water quality during base-flow (conditions generally representing only groundwater discharge) and storm-runoff conditions in four tributaries to the Cambridge and Stony Brook Reservoirs and in the main stem of Stony Brook, the primary source of inflow to the Stony Brook Reservoir (Smith, 2013). Currently (2015), the USGS, in cooperation with the CWD, operates water-quality monitoring stations on every major tributary and on the three reservoirs in the drinking-water source area. The City of Cambridge Drinking-Water Supply SystemThe CWD supplies approximately 15 million gallons per day of drinking water to more than 100,000 customers. The CWD obtains raw water from a serial system of three primary storage reservoirs-Cambridge Reservoir (also known as the Hobbs Brook Reservoir), Stony Brook Reservoir, and Fresh Pond Reservoir-in parts of Cambridge, Lexington, Lincoln, Waltham, and Weston, Mass. (fig. 1). These reservoirs receive inflow from a source area of 23.7 square miles. The Cambridge drinking-water source area contains major transportation corridors (Interstate 95, State Routes 2, 2A, 20, and 117) as well as large impervious areas of industrial, commercial, and residential land use ( fig. 2). Only about 5 percent of this land is owned by Cambridge. The watershed for the Cambridge Reservoir includes Hobbs Brook and three unnamed tributaries that AbstractDuring 2005-8, the U.S. Geological Survey, in cooperation with the Cambridge, Massachusetts, Water Department, measured concentrations of sodium and chloride, plant nutrients, commonly used pesticides, and caffeine in base-flow and stormwater samples collected from 11 tributaries in the Cambridge drinking-water source area. These data were used to characterize current water-quality conditions, to establish a baseline for future comparisons, and to describe trends in surface-water quality. The data also were used to assess the effects of watershed characteristics on surface-water quality and to inform future watershed management.