These geospatial data sets consist of contours derived from surface grids of precipitation depths for seven frequencies at 12 durations used in a regional precipitation frequency analysis for Oklahoma. Eighty-four depth-duration-frequency contour maps were produced from precipitation-station data. The contour interval varies from 0.05 to 0.5 inch.

Data were used from precipitation gage stations with at least 10 years of record within Oklahoma and about 50 kilometers into bordering states. Data were analyzed for seven frequencies (expressed as recurrence intervals of 2-, 5-, 10-, 25-, 50-, 100-, and 500-years) and 12 durations (15-, 30-, and 60-minutes; 1-, 2-, 3-, 6-, 12-, and 24-hours; and 1-, 3-, and 7-days).

Statistical methods were used to estimate precipitation depths for each duration-frequency at each station. These station depth-duration-frequency estimates were interpolated to produce continuous grids with grid-cell spacing of 2,000 meters. Contour lines derived from these surfaces (grids) were used to produce the maps in the "Depth-Duration Frequency of Precipitation for Oklahoma," by R.L. Tortorelli, Alan Rea, and W.H. Asquith, U.S. Geological Survey Water-Resources Investigations Report 99-4232.