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Precipitation Frequency Data

Precipitation frequency data for most of the United States can be downloaded from the NOAA or NRCC web sites.  Equivalent data for other locations, including sites outside the United States, may be available from the applicable weather bureau.  Most data that can be provided in the standard NOAA format or any of the prior HydroCAD IDF formats is suitable for use with HydroCAD.

Precipitation Data for Other Locations

Precipitation data for other locations, including international applications, is generally available from the applicable weather bureau.  In order to be directly compatible with HydroCAD, files must use one of the standard NOAA formats shown below: 

Point precipitation frequency estimates (inches)   Current NOAA format download sample here
NOAA Atlas 14, Volume 1, Version 3
Data type: Precipitation depth
Time series type: Partial duration
Project area: Southwest
Latitude (decimal degrees): 34.7294
Longitude (decimal degrees): -114.5075

PRECIPITATION FREQUENCY ESTIMATES
by duration for ARI (years):, 1,2,5,10,25,50,100,200,500,1000
5-min:, 0.11,0.16,0.24,0.32,0.43,0.53,0.65,0.79,1.01,1.20
10-min:, 0.17,0.24,0.37,0.48,0.66,0.81,0.99,1.20,1.53,1.83
15-min:, 0.21,0.29,0.46,0.60,0.82,1.01,1.23,1.49,1.90,2.27
30-min:, 0.29,0.40,0.62,0.81,1.10,1.36,1.66,2.01,2.56,3.06
60-min:, 0.36,0.49,0.77,1.00,1.36,1.68,2.05,2.48,3.16,3.79
2-hr:, 0.43,0.58,0.89,1.16,1.56,1.91,2.32,2.79,3.52,4.17
3-hr:, 0.47,0.64,0.97,1.24,1.65,2.01,2.42,2.89,3.65,4.34
6-hr:, 0.57,0.76,1.14,1.44,1.87,2.24,2.66,3.11,3.89,4.58
12-hr:, 0.67,0.90,1.32,1.65,2.13,2.52,2.94,3.39,4.09,4.78
24-hr:, 0.81,1.06,1.50,1.83,2.31,2.70,3.11,3.55,4.17,4.83
2-day:, 0.86,1.12,1.52,1.85,2.33,2.73,3.14,3.59,4.22,4.88

NOAA Atlas 14 Precipitation frequency estimates (inches)   Previous NOAA format download sample here
Point Estimates
Data series, Partial duration maxima
State, Maryland
Station, Montgomery
Lon (dd), -77.2120
Lat (dd), 39.1913
Elev (feet), 406
MEAN PRECIPITATION FREQUENCY ESTIMATES
Freq (yr),5-min,10-min,15-min,30-min,60-min,120-min,3-hr, 6-hr, 12-hr, 24-hr,  2-day
   1,     0.34,  0.54,  0.68,  0.93,  1.16,  1.37,  1.48, 1.82,  2.23,  2.57,  2.98
   2,     0.41,  0.65,  0.82,  1.13,  1.42,  1.67,  1.79, 2.21,  2.69,  3.10,  3.61
   5,     0.48,  0.78,  0.98,  1.40,  1.79,  2.12,  2.27, 2.79,  3.41,  3.99,  4.62
  10,     0.54,  0.87,  1.10,  1.59,  2.07,  2.47,  2.66, 3.27,  4.02,  4.77,  5.49
  25,     0.61,  0.98,  1.24,  1.84,  2.45,  2.97,  3.21, 3.98,  4.96,  5.97,  6.81
  50,     0.67,  1.06,  1.35,  2.03,  2.75,  3.39,  3.67, 4.59,  5.79,  7.03,  7.95
 100,     0.72,  1.15,  1.45,  2.22,  3.06,  3.83,  4.17, 5.25,  6.72,  8.23,  9.22
 200,     0.77,  1.23,  1.55,  2.41,  3.38,  4.30,  4.70, 5.97,  7.75,  9.60, 10.64
 500,     0.84,  1.33,  1.68,  2.66,  3.82,  4.97,  5.46, 7.05,  9.34, 11.70, 12.79
1000,     0.90,  1.41,  1.77,  2.86,  4.17,  5.53,  6.10, 7.96, 10.71, 13.55, 14.63

 

Notes:

1) Additional spacing has been added to these examples for readability.

2) The file does not have to contain all the specific frequencies shown in this example.  You can add or omit lines or columns for the specific frequencies of interest.

3) The durations can be changed or omitted depending on the available data.  Duration values beyond the intended storm duration (e.g. 24-hours) are not required and can be omitted.  When data is limited, intermediate durations can also be omitted.  A minimum of three durations are generally recommended, including 5-minutes, 60-minutes, and 24-hours.

4) Depth values may be specified in inches or millimeters, and will be automatically converted by HydroCAD as required by the individual project settings.  The units in your data file do not have to match the project units.

 

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