The regime of dry‐weather flow of several streams in Ohio is presented by flow‐duration curves. For comparison, the index of ground‐water flow for each basin is the discharge in cubic feet per second per square mile which is exceeded 90 per cent of the time. These indices are shown on a map of Ohio, and are discussed with respect to known geological conditions. It is concluded that stream‐flow records provide useful inferences to ground‐water geology, but the converse is not true.