INTRODUCTION The Water Resources Division of the U.S. Geological Survey, in cooperation with State agencies, obtains a large amount of data pertaining to the water resources of Massachusetts and Rhode Island each water year. These data, accumulated during many water years, constitute a valuable data base for developing an improved understanding of the water resources of the States. To make these data readily available to interested parties outside the Geological Survey, the data are published annually in this report series entitled 'Water Resources Data-Massachusetts and Rhode Island.' Hydrologic data are also available through the Massachusetts-Rhode Island District Home Page on the world-wide web (http://ma.water.usgs.gov). Historical data and real-time data (for sites equipped with satellite gage-height telemeter) are also available. The home page also contains a link to the U.S. Geological Survey National Home Page where streamflow data from locations throughout the United States can be retrieved. This report series includes records of stage, discharge, and water quality of streams; contents of lakes and reservoirs; water levels of ground-water wells; and water quality of ground-water wells. This volume contains discharge records at 90 gaging stations; stage records at 2 gaging stations; monthend contents of 4 lakes and reservoirs; water quality at 31 gaging stations; water quality at 27 observation wells; and water levels for 139 observation wells. Locations of these sites are shown in figures 1 and 2. Short-term water-quality data were collected at 21 gaging stations and 27 observation wells and are shown in figure 3. Miscellaneous hydrologic data were collected at various sites that were not involved in the systematic data-collection program and are published as miscellaneous discharge measurements. The data in this report represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State and Federal agencies in Massachusetts and Rhode Island. This series of annual reports for Massachusetts and Rhode Island began with the 1961 water year with a report that contained only data relating to the quantities of surface water. For the 1964 water year, a similar report was introduced that contained only data relating to water quality. Beginning with the 1975 water year, the report format was changed to present, in one volume, data on quantities of surface water, quality of surface and ground water, and ground-water levels. Prior to introduction of this series and for several water years concurrent with it, water-resources data for Massachusetts and Rhode Island were published in U.S. Geological Survey Water-Supply Papers. Data on stream discharge and stage and on lake or reservoir contents and stage, through September 1960, were published annually under the title 'Surface-Water Supply of the United States, Parts 1A and 1B.' For the 1961 through 1970 water years, the data were published in two 5-year reports. Data on chemical quality, temperature, and suspended sediment for the 1941 through 1970 water years were published annually under the title 'Quality of Surface Waters of the United States,' and water levels for the 1939 through 1974 water years were published under the title 'Ground-Water Levels in the United States.' The above mentioned Water-Supply Papers may be consulted in the libraries of the principal cities of the United States and may be purchased from U.S. Geological Survey, Information Services, Box 25286, Denver Federal Center, Box 25425, Denver, CO 80225-0286. Publications similar to this report are published annually by the Geological Survey for all States. These official Survey reports have an identification number consisting of the two-letter State abbreviation, the last two digits of the water year, and the volume number. For example, this volume is identified as 'U.S. Geological Survey Water-Data Report MARI-98-1.' For archiving and general d