Digital Data Sets of Depth-Duration Frequency of Precipitation For Oklahoma

These geospatial data sets were produced as part of a regional precipitation
frequency analysis for Oklahoma. The data sets consist of surface grids of
precipitation depths 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).
Eighty-four depth-duration-frequency surfaces were produced from
precipitation-station data. Precipitation-station data from which the surfaces
were interpolated and contour lines derived from each surface also are
included. Contour intervals vary from 0.05 to 0.5 inch.

Data were used from precipitation gage stations with at least 10 years of
record within Oklahoma and a zone extending about 50 kilometers into bordering
states. Three different rain gage networks provided the data (15-minute,
1-hour, and 1-day). Precipitation annual maxima (depths) were determined from
the station data for each duration for 110 15-minute, 141 hourly, and 413 daily
stations. 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. The geospatial data sets
are presented in digital form for use with geographic information systems.
These geospatial data sets may be used to determine an interpolated value of
depth-duration-frequency of precipitation for any point in Oklahoma.

[Summary provided by USGS.]