Redd Count

The chart below provides total annual fall Chinook redd counts by year from 1991 through 2015. The redd counts were collected from aerial surveys conducted by Idaho Power, the U.S. Fish & Wildlife Service and the Nez Perce Tribe for the Snake, Grande Ronde and Imnaha rivers during the noted spawning period.

For more detailed information about redd counts during each year, click the year in the table below.

Total Redd Count By Year
Year Snake River Grande Ronde River Imnaha River Clearwater River Salmon River Total
2015  3,155  378 83 5,081 142  8,839
2014 2,808 342 103 3,078 42 6,373
2013 2,667 255 38 2,956 31 5,947
2012 1,828 303 85 1,654 34 3,904
2011 2,837 154 24 1,611 60 4,686
2010 2,944 263 132 1,642 8 4,989
2009 2,095 101 36 1,198 34 3,464
2008 1,819 185 68 949 14 3,035
2007 1,117 80 17 718 18 1,950
2006 1,025 41 36 257 9 1,368
2005 1,442 129 36 487 27 2,121
2004 1,709 161 35 630 21 2,556
2003 1,524 84 44 571 18 2,241
2002 1,113 111 72 524 31 1,851
2001 710 197 38 312 22 1,279
2000 346 8 9 184 0 536
1999 373 13 9 184 0 579
1998 185 24 13 78 3 303
1997 58 55 3 72 1 189
1996 113 20 3 69 1 206
1995 71 18 4 20 2 115
1994 67 15 0 37 1 120
1993 127 49 4 36 3 219
1992 47 5 3 26 1 82
1991 47 0 4 4 0 55

Idaho Power’s Fall Chinook Program began in 1991 and is a voluntary operations plan for the Hells Canyon Complex.

The program provides a stable river flow level during the fall Chinook salmon spawning period, generally from mid-October to early December. The flow level provided during the fall Chinook salmon spawning period generally establishes what the minimum flow from Hells Canyon Dam will be once spawning is complete.

Minimum Flows

This minimum flow may be slightly lower than the stable flow provided during the spawning period. The minimum flow depends on the depth of the shallowest redds observed during the spawning period. The minimum flow level is the level that will protect the shallowest redd in the Snake River from being dewatered. Dewatering is when there is not enough water to sufficiently cover the redds.

Idaho Power maintains this minimum flow throughout the entire incubation and emergence period, which is approximately the end of May. The emergence period is when the fish swim up out of the redds. The stable flow level provided during the spawning period may vary from one year to the next. The flow level depends on the quantity of water available, which largely depends on the amount of snow pack within a given water year.

Redd Counts

The U.S. Fish & Wildlife Service and Idaho Power started a cooperative research program to determine the quantity of spawning habitat and flow levels necessary to support sufficient spawning habitat for fall Chinook salmon. As part of this research program, fall Chinook salmon redd counts happen each year.

Redd counts monitor redd locations and establish the location and depth of the shallowest redd. Idaho Power and the U.S. Fish and Wildlife Service do weekly counts via helicopter during the spawning period over the Snake River. In addition, the Nez Perce Tribe conducts aerial redd counts on the Clearwater, Grande Ronde, Imnaha and Salmon Rivers.

These survey flights account for the majority of the redds observed. However, in the Snake River, many redds cannot be observed from the air because they are in deep water. So, deep water redd searches using underwater videography occur during the spawning period as well as the aerial surveys. Redds as deep as 22 feet have been observed in the Snake River using underwater videography.