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 survival. 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. It was then subsetted to only include large catchments (90-120 sqkm).
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
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 large catchments (90-120 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.

File Upload

Steelhead - MAD CEMPRA SR Function (393.07 KB)

Steelhead - MAD SR documentation (182.11 KB)

Grantham et al 2012 LOW FLOWS, LANDUSE AND JUVENILE STEELHEAD OVER SUMMER SURVIVAL IN CALIF STREAMS_1.pdf (781.56 KB)

Images

Stressor Response csv data

Data_Steelhead_Flow_Cali_L_0.csv (1.49 KB)

PERCENT_MAD	Mean System Capacity (%)	up.limit
0.53791	28.9807491	100
0.54323	29.0180423	100
0.54504	29.0307304	100
0.55888	29.1277488	100
0.56427	29.1655327	100
0.78606	30.7202806	100
0.78937	30.7434837	100
0.79821	30.8054521	100
0.92197	31.6730097	100
0.9271	31.708971	100
0.93066	31.7339266	100
0.93434	31.7597234	100
0.95858	31.9296458	100
0.96561	31.9789261	100
1.19094	33.5584894	100
1.36019	34.7449319	100
1.36897	34.8064797	100
1.47038	35.5173638	100
1.47382	35.5414782	100
1.4772	35.565172	100
1.48215	35.5998715	100
1.51707	35.8446607	100
1.53282	35.9550682	100
1.5958	36.396558	100
1.60272	36.4450672	100
1.86155	38.2594655	100
1.86497	38.2834397	100
1.86657	38.2946557	100
2.04641	39.5553341	100
2.04804	39.5667604	100
2.43258	42.2623858	100
2.43773	42.2984873	100
2.4999	42.734299	100
2.50359	42.7601659	100
2.50866	42.7957066	100
2.51062	42.8094462	100
2.5159	42.846459	100
3.19539	47.6096839	100
3.19766	47.6255966	100
3.2	47.642	100
3.89758	52.5320358	100
3.89968	52.5467568	100
3.90172	52.5610572	100
3.91877	52.6805777	100
3.91884	52.6810684	100
3.92541	52.7271241	100
4.16129	54.3806429	100
4.16359	54.3967659	100
4.16561	54.4109261	100
4.17467	54.4744367	100
4.3259	55.534559	100
5.00106	60.2674306	100
5.00991	60.3294691	100

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Mean Annual Discharge and Steelhead

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