A model of the effects of flow fluctuations on fall Chinook salmon spawning habitat availability in the Columbia River
Previously we reported that about 30% to 60% of the area predicted to be used by fall Chinook salmon (Oncorhynchus tshawytscha) for spawning in the Hanford Reach of the Columbia River did not contain redds. One explanation for the overprediction of habitat was that our model did not incorporate streamflow fluctuation. Daily fluctuation in flow caused by load-following operations (power generation to meet short-term electrical demand) at Priest Rapids Dam, situated at the upper end of the Hanford Reach, changes the hydraulic characteristics to which fish respond in selecting redd sites. The purpose of the study described here was to examine the effect of flow changes on spawning habitat modeling and, in particular, to look at the connection between spawning and the variability and persistence of habitat variables caused by rapid changes in flow resulting from load-following operations at Priest Rapids Dam. We found that spawning habitat use by fall Chinook salmon was consistent with previous fall Chinook salmon studies in the Reach. Dynamic variables that were based on hourly time series were used to account for the variability in habitat as a result of flow fluctuations. The analysis showed that the proportion of velocities that fell within the range of 1.0 to 2.5 m/s differed significantly between locations that were predicted to be spawning by the logistic regression model where spawning actually occurred and locations that were predicted to be spawning where spawning did not occur. However, the resulting sequential logistic regression model that incorporated the dynamic variables did not provide significant improvement in the percentage of errors for areas predicted to be spawning; the model’s overprediction errors still ranged from 63% to 78%. We suggest that while flow fluctuation may affect spawning habitat and individual fish behavior, the high correlation between time-averaged velocities and the proportion of hourly velocities that fell within the most favorable range negated any improvements in model predictions.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 949918
- Report Number(s):
- PNNL-SA-55022; 400480000; TRN: US200909%%475
- Journal Information:
- North American Journal of Fisheries Management, 28(6):1894-1910, Vol. 28, Issue 6
- Country of Publication:
- United States
- Language:
- English
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