The US Geological Survey (USGS) collects hydrologic data from 1332 stream, lake, and ground-water sites in Oklahoma. Information on the quantity of water from a network of 123 streamflow stations, 30 lakes, 42 peak-flow stations, three low-flow stations, and on the quality of water from 40 stream locations is published each year in the USGS publication Water Resources Data for Oklahoma. Information on water levels from 1134 ground-water wells is currently published in cooperation with the State of Oklahoma in the USGS publication Ground-Water Levels in Observation Wells in Oklahoma. The data also are made available to the public as printouts from several computerized databases maintained by the USGS. -Author