This map scale 1:125,000 presents a preliminary assessment of the availability of ground water in the lower Connecticut River basin in southwestern New Hampshire. It is a generalization of several hydrogeologic factors and provides a guideline for ground-water exploration useful in water- and land-use planning. It does not describe the absolute quantity or quality of ground water available. The best aquifers in the basin are deposits of stratified sand or sand and gravel of Pleistocene age. Large aquifers of this type occur in places in the Connecticut River valley and in valleys of tributaries to the Connecticut River. Ground water is generally of good chemical quality. Iron and manganese in concentrations greater than the recommended limits for drinking water suggested by the U.S. Public Health Service are not uncommon. (USGS).