Carol Kendall Tyler B. Coplen 2000 Increasingly, hydrologic studies require information on the isotopic composition of natural waters. This report presents stable hydrogen (delta2H) and oxygen isotope ratios (delta18O) from 391 selected sites of the U.S. Geological Survey's National Stream Quality Accounting Network (NASQAN) and BENCHMARK surface water networks collected during the years 1984-1987. Depth-integrated samples were collected and analyzed from each site bimonthly or quarterly for about 3 years. application/pdf 10.3133/ofr00160 en U.S. Dept. of the Interior, U.S. Geological Survey ; Branch of Information Services [distributor], Stable hydrogen and oxygen isotope ratios for selected sites of the U.S. Geological Survey's NASQAN and benchmark surface-water networks reports