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The RASA Program represents a systematic effort to study a number of the Nation's most important aquifer systems, which, in aggregate, underlie much of the country and which represent an important component of the Nation's total water supply. In general, the boundaries of these studies are identified by the hydrologic extent of each system and, accordingly, transcend the political subdivisions to which investigations have often arbitrarily been limited in the past. The broad objective for each study is to assemble geologic, hydrologic, and geochemical information, to analyze and develop an understanding of the system, and to develop predictive capabilities that will contribute to the effective management of the system. The use of computer simulation is an important element of the RASA studies to develop an understanding of the natural, undisturbed hydrologic system and the changes brought about in it by human activities and to provide a means of predicting the regional effects of future pumping or other stresses. The final interpretive results of the RASA Program are presented in a series of U.S. Geological Survey Professional Papers that describe the geology, hydrology, and geochemistry of each regional aquifer system. Each study within the RASA Program is assigned a single Professional Paper number beginning with Professional Paper 1400.

water-quality characteristics and constituents of samples from U.S. Geological Survey gaging stations 22. Bimonthly (summer) means of selected water-quality characteristics and constituents of samples from U.S. Bureau of Reclamation data-collection areas 23. Bimonthly (summer) means of selected water-quality characteristics and constituents of samples from areas within the Arrowwood National Wildlife Refuge, North Dakota 24. Number of measurements of water-quality characteristics

Introduction 1 Background 1 Purpose Reaches used 1n the salinity model Developing d1ssolved-so!1ds data for the salinity model Dissolved sol Ids as a measure of salinity Historical data Correlation of dissolved sol Ids with specific conductance Correlation of specific conductance with streamflow Dissolved sol Ids of supplemental surface-water sources James River upstream of Grace City, N.Dak. Lake Audubon, N.Dak., at Snake Creek pumping station Pipestem Creek, N.Dak. Elm River system in South Dakota Dissolved solids of significant groundwater sources