Guidelines for Fish Passage Flows

 

Several states have defined flows at which fish passage should be provided, except for Alaska and Idaho these requirements apply only to hydraulic designs (not stream simulation).

State and Agency Flow Guidelines for Fish Passage Flows

State / Agency

High Flow Capacity

High Fish Passage Flow

Low Fish Passage Flow

Alaska

Q50 or Q100

"Q2d2" the flow 24 hours before or after the 2-yr flood

None

Washington

Q100

w/ debris

10% exceedance flow during migration period: species specific

2-yr, 7-day low flow

 

Oregon

 

Q100

 

10% exceedance flow during migration period: species specific. Approximate by Q10% = 0.18*(Q2)+36 where Q2>44 cfs. where Q2<44 cfs use Q2

2-yr, 7-day low flow or 95% exceedance flow for migration period: species specific

NMFS SW Region

Q100

at HW/D =1

for adult salmon & steelhead 1% annual exceedance flow or 50% Q2. For juveniles, 10% annual exceedance flow

for adult salmon & steelhead, the greater of 3 cfs or 50% annual exceedance flow. For juveniles, the greater of 95% annual exceedance flow or 1 cfs.

California Dept. Fish & Game

Q100

at HW/D =1.5

standards vary from 1%-10% annual exceedance for various groups of fish

standards vary from 50%-95% annual exceedance for various groups of fish

NMFS NW Region

 

5% exceedance flow for period of upstream migration

95% exceedance flow during months of upstream migration

Idaho

 

 

 

Maine

 

 

 

Q100 is the peak flow equaled or exceeded on average once in 100 years. Determined based on annual peak flow data set.

10% exceedance flow during the migration period is the daily average flow that is equaled or exceeded 10% of the days in the period the selected fish species are moving. That period is usually established by the state fish and wildlife management agency. Based on period of record daily-flow data set for the migration period.

1% annual exceedance flow is the daily average flow that is equaled or exceeded 1% of the days of the year. Determined based on period of record daily mean flow data set for the entire year.