Mean Annual Discharge and Steelhead

Species Common Name

Steelhead

Latin Name (Genus species)

Oncorhynchus mykiss irideus

Stressor Name

Flow

Specific Stressor Metric

Mean Annual Discharge (MAD)

Stressor Units

%

Vital Rate (Process)

Over-summer survival

Life Stage

Juvenile

Season

Summer

Geography

Maacama Creek, Mark West Creek, Santa Rosa Creek, Green Valley Creek. California, USA

Detailed SR Function Description

Final curve was derived from a linear regression.

System capacity was derived from oversummer survival with data spanning years 1994-2002. The original data points represent 50-55 sites yielding 523 observations where oversummer surviva. Survival was estimated by sampling twice, in midsummer and late summer through repeated census counts using pole seins and blocking nets were used until no fish were captured (typically 3-5 passes) which were then sorted as species then counted.
To normalize and rescale each ecological response, each value was scaled by the maximum ecological response observed in the study such that mean habitat capacity percentage (normalized response) = response / maximum ecological response observed.
Note: Only used 75th percentile data in overall analysis because 10th percentile flows are extremely small. SR function represents medium catchments.
Implicit pathway of effect: Oversummer survival of juvenile steelhead increases with higher summer discharge

Function Derivation

Observational data. Final curve was derived from linear regression.

Transferability of Function

Appropriate for summer stream flow impacts on over-summer survival of juvenile steelhead. General transferability to other salmon stocks in unclear, but likely appropriate for other spring-spawning salmonids (i.e., regions with similar hydrology to the Maacama Creek, Mark West Creek, Santa Rosa Creek, Green Valley Creek system).
The relationship may be unreliable if extrapolated to a flow range outside the original data (see the Average Salmonid flow-ecology SR function entry based on Rosenfeld and Enright (2025) for a more generalizable function across a wider range of flows).

Note: This entry reflects only the subset including medium catchments (40-90 sqkm), see other entries for other catchment sizes.

Source of stressor Data

The summer streamflow data (discharge) for each reach during the 9 years of sampling was estimated by the original authors (Grantham et al. 2012) based off a rain-fall run-off regression model based off of daily rainfall records. Data was sourced from the U.S. Geological Survey. Estimates was scaled by reach area. Estimates were later validated with measured flows at all sites with at least 12 measurements. See Grantham et al. 2012 for further details.
Data was then standardized by dividing absolute flow by MAD to achieve %MAD values (see Rosenfeld & Enright 2024). Such standardization allows for comparison of flow metrics across a wide range of stream sizes (see Rosenfeld et al. 2017).

Function Type

continuous

Stressor Scale

linear

References Cited

Grantham, T.E., Newburn, D.A., McCarthy, M.A., and Merenlender, A.M. 2012. The role of streamflow and land use in limiting oversummer survival of juvenile steelhead in California streams. Trans. Am. Fish. Soc. 141:585-598.

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Steelhead - MAD CEMPRA SR Function (410.64 KB)

Steelhead - MAD SR documentation (185.99 KB)

Grantham et al 2012 LOW FLOWS, LANDUSE AND JUVENILE STEELHEAD OVER SUMMER SURVIVAL IN CALIF STREAMS_0.pdf (781.56 KB)

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Stressor Response csv data

Data_Steelhead_Flow_Cali_M_0.csv (1.92 KB)

PERCENT_MAD	Mean System Capacity (%)	up.limit
0.6601	50.043305	100
0.6631	50.052455	100
0.66987	50.0731035	100
0.85964	50.651902	100
0.86415	50.6656575	100
0.86663	50.6732215	100
0.86666	50.673313	100
0.87754	50.706497	100
0.88402	50.726261	100
1.17291	51.6073755	100
1.18126	51.632843	100
1.18134	51.633087	100
1.18268	51.637174	100
1.18697	51.6502585	100
1.23652	51.801386	100
1.45809	52.4771745	100
1.50269	52.6132045	100
1.50298	52.614089	100
1.51016	52.635988	100
1.51021	52.6361405	100
1.51662	52.655691	100
1.57039	52.8196895	100
1.5719	52.824295	100
1.57312	52.828016	100
1.58179	52.8544595	100
1.59	52.8795	100
1.85929	53.7008345	100
1.86198	53.709039	100
1.86456	53.716908	100
2.09807	54.4291135	100
2.10072	54.437196	100
2.10146	54.439453	100
2.10238	54.442259	100
2.10317	54.4446685	100
2.2719	54.959295	100
2.27529	54.9696345	100
2.27551	54.9703055	100
2.28156	54.988758	100
2.28408	54.996444	100
2.28562	55.001141	100
2.2909	55.017245	100
2.91219	56.9121795	100
2.91456	56.919408	100
2.91459	56.9194995	100
2.91576	56.923068	100
3.14616	57.625788	100
3.14741	57.6296005	100
3.15263	57.6455215	100
3.15278	57.645979	100
3.79367	59.6006935	100
3.79446	59.603103	100
3.79593	59.6075865	100
5.11091	63.6182755	100
5.1153	63.631665	100
5.11649	63.6352945	100
5.11654	63.635447	100
5.34772	64.340546	100
5.34893	64.3442365	100
5.34915	64.3449075	100
5.35076	64.349818	100
5.35363	64.3585715	100
6.0774	66.56607	100
6.0808	66.57644	100
6.08455	66.5878775	100
6.0877	66.597485	100
6.08791	66.5981255	100
6.08823	66.5991015	100
6.09181	66.6100205	100
6.09193	66.6103865	100
6.09551	66.6213055	100

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Mean Annual Discharge and Steelhead

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