Calcium, sodium, sulfate, and chloride in stream water of the western conterminous United States to 1957

This Hydrologic Atlas shows concentrations of calcium, sodium (or sodium plus potassium), sulfate, and chloride in stream water of 11 of the Western States, regardless of the sources from which the mineral constituents came. The maps are, in a sense, a historical summary, showing concentrations observed to 1956 and reported in published references. Data on chemical quality of stream water has been obtained at various times and at various places; for no single year does the record even approach complete coverage of the area shown on the maps. It was necessary, therefore, to combine the records of many years in order to achieve this summary.