Northern Prairie Wildlife Research Center
| Period |
Flow (CFS) |
Duration (Days) | Frequency (Yrs) Exceedence (%) | |
| Very Wet | May 1 - June 30* | >16000 | 5** | 1 in 5 (20%) |
| Wet | May 1 - June* | > 12000 | 5** | 1 in 2.5 (40%) |
| Normal | May 20 - June 20 | > 3000 | 7-30*** | 3 in 4 (75%) |
| Dry | May 11 - June 30 | none**** | all remaining (100%) |
* At least 50% of these pulse flows should occur during May 20 to June 20,
with May 1 to June 30 as the timeframe for broadest benefit for channel maintenance,
and instream and wet meadow habitats. Occurrence between February 1 and June
30 would accomplish the necessary effects for channel maintenance. The 10-year
running average for the mean annual pulse flow targets should range from approximately
8,300 cfs to 10,800 cfs.
** The duration of these pulse flows should emulate the historic, natural
pattern: (a) ascended over approximately 10 days, (b) cresting for approximately
5 days, and (c) descending over approximately 12 days.
*** The target is for a 10-year running average for the 30-day exceedence
flow (i.e., 10-year running average of the annual level exceeded for 30 consecutive
days) of at least 3,400 cfs. A flow of 3,000 cfs should be exceeded for 7-30
days in at least 75% of years. Pulse flows should be followed by descending
flows approximating a rate of 800 cfs/day.
**** No pulse flows during May and June in driest years; target flows identified
in (Bowman 1994), apply under dry year conditions.
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/habitat/plrivmgt/table14.htm
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Page Last Modified: Saturday, 02-Feb-2013 04:53:29 EST
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