The Charles River basin encompasses about 300 square miles of gently rolling to hilly terrain, with altitudes ranging from 586 feet in Hopkinton to below 10 feet in Boston, Mass. The area is essentially urban, although the towns in the upper basin still retain some rural character. The population of the middle and upper parts increased 80 percent between 1950 and 1970, while the population in the lower part declined 4 percent. This atlas summarizes the water resources and associated water problems of the area. The investigation upon which the atlas is based was made from 1968 to 1971 and is part of a series covering the major river basins in Massachusetts. The study area includes 251 sq mi of drainage area above the gaging station at Waltham. (Woodard-USGS)