In the development of rainfall frequency and volume data for Minnesota, the Minnesota Stormwater Manual Sub-Committee conducted an analysis of rainfall distribution for several locations in Minnesota. The methodology and results of this analysis are described in Issue Paper B. Frequency-volume graphs were developed for several locations in the state and are illustrated below.

In viewing these graphs, note that the volume represents the percent volume captured for a particular size storm and not the cumulative volume. For example, consider a BMP designed to capture the first inch of precipitation. A 1 inch storm captures about 90 percent of all rainfall events at Minneapolis-St. Paul International Airport. Storms up to 1 inch represent about 60 percent of the total volume. However, for storms exceeding 1 inch in depth, the first inch will be captured by the BMP. Thus, the annual volume captured by the BMP is much greater than 60 percent. For a B soil, the annual volume captured by the BMP will be about 90 percent. The table below summarizes annual volume captured by a BMP at the Minneapolis-St. Paul International Airport for different soil types.

Annual volume, expressed as a percent of annual runoff, treated by a BMP as a function of soil and water quality volume. See footnote1 for how these were determined.
Link to this table

Soil Water quality volume (VWQ) (inches)
0.5 0.75 1.00 1.25 1.50
A (GW) 84 92 96 98 99
A (SP) 75 86 92 95 97
B (SM) 68 81 89 93 95
B (MH) 65 78 86 91 94
C 63 76 85 90 93

1Values were determined using the MIDS calculator. BMPs were sized to exactly meet the water quality volume for a 2 acre site with 1 acre of impervious, 1 acre of forested land, and annual rainfall of 31.9 inches.


map showing rainfall frequency and volume percentiles as a function of precipitation depth for Cloquet map showing rainfall frequency and volume percentiles as a function of precipitation depth for Fargo map showing rainfall frequency and volume percentiles as a function of precipitation depth for Grand Forks map showing rainfall frequency and volume percentiles as a function of precipitation depth for Grand Marais map showing rainfall frequency and volume percentiles as a function of precipitation depth for Itasca map showing rainfall frequency and volume percentiles as a function of precipitation depth for Lamberton map showing rainfall frequency and volume percentiles as a function of precipitation depth for Minneapolis and St. Paul map showing rainfall frequency and volume percentiles as a function of precipitation depth for Rochester map showing rainfall frequency and volume percentiles as a function of precipitation depth for St. Cloud map showing rainfall frequency and volume percentiles as a function of precipitation depth for Thief River Falls

This page was last modified on 28 December 2015, at 10:24.

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