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Interacting effects of minimum flow and fluctuating shorelines on benthic stream insects. Research technical completion report, project no. A-052-IDA Item Info

A 50 mile (80 km) reach of the Clearwater River, Idaho was studied from its confluence with the Snake River upstream to Orofino, Idaho. The study examined two important changes in the River: 1) effects of hydropower releases from Dworshak Dam on the aquatic insect community in the free flowing reach of the Clearwater River, and 2) backwater effects of Lower Granite Dam on benthos in the lower five miles (8 km) of the Clearwater River. As result of the operational mode of Dworshak Dam, late summer and fall flows are greater than during the pre-project era. Although hydropower releases cause frequent and marked fluctuations in discharge, there is a stable post project low flow. This higher late summer flow guarantees the submergence of additional substrate, thereby increasing macrobenthic habitat. Over 120 species of aquatic insects exclusive of Chironomidae have been collected from the Clearwater River. While small to moderate shifts in seasonal densities of principal species have occurred between intensive study sites above and below the influence of Dworshak Dam, present evidence does not indicate these shifts are attributable to hydropower releases. Approximately one month was required for sterile rocks to support a standing crop similar to that of continually watered rocks. In most instances, numbers of species and densities increased with increasing depth of 15, 30 and 45 cm. Numbers of drifting insects were greatest during the nights. Drift rates and standing crop relationships above and below the influence of Dworshak Dam suggest insects drifted more in response to daily fluctuations than to the factor of bottom density. Within the lower five miles of the Clearwater, variable backwater effects of Lower Granite Reservoir have a far more pronounced effect on the amount of potential benthic habitat available than do releases from Dworshak Dam. Formation of Lower Granite reservoir has resulted in insect community shifts from a riverine to a lentic community as a result of physical changes in water depth, velocity and substrate with dipteran midges the dominant insect group.

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Title:
Interacting effects of minimum flow and fluctuating shorelines on benthic stream insects. Research technical completion report, project no. A-052-IDA
Authors:
Brusven, Merlyn; Trihey, E. Woody
Date Created (ISO Standard):
1978-08
Description:
A 50 mile (80 km) reach of the Clearwater River, Idaho was studied from its confluence with the Snake River upstream to Orofino, Idaho. The study examined two important changes in the River: 1) effects of hydropower releases from Dworshak Dam on the aquatic insect community in the free flowing reach of the Clearwater River, and 2) backwater effects of Lower Granite Dam on benthos in the lower five miles (8 km) of the Clearwater River. As result of the operational mode of Dworshak Dam, late summer and fall flows are greater than during the pre-project era. Although hydropower releases cause frequent and marked fluctuations in discharge, there is a stable post project low flow. This higher late summer flow guarantees the submergence of additional substrate, thereby increasing macrobenthic habitat. Over 120 species of aquatic insects exclusive of Chironomidae have been collected from the Clearwater River. While small to moderate shifts in seasonal densities of principal species have occurred between intensive study sites above and below the influence of Dworshak Dam, present evidence does not indicate these shifts are attributable to hydropower releases. Approximately one month was required for sterile rocks to support a standing crop similar to that of continually watered rocks. In most instances, numbers of species and densities increased with increasing depth of 15, 30 and 45 cm. Numbers of drifting insects were greatest during the nights. Drift rates and standing crop relationships above and below the influence of Dworshak Dam suggest insects drifted more in response to daily fluctuations than to the factor of bottom density. Within the lower five miles of the Clearwater, variable backwater effects of Lower Granite Reservoir have a far more pronounced effect on the amount of potential benthic habitat available than do releases from Dworshak Dam. Formation of Lower Granite reservoir has resulted in insect community shifts from a riverine to a lentic community as a result of physical changes in water depth, velocity and substrate with dipteran midges the dominant insect group.
Subjects:
benthos dam effects hydroelectric plants
Location:
Clearwater River
Latitude:
46.5
Longitude:
-116.69
Collection:
IWRRI
Series:
Water for Idaho
IWRRI number:
197803
Rights:
Rights to the digital resource are held by the University of Idaho. http://www.uidaho.edu/
Publisher:
University of Idaho
Contributing Institution:
University of Idaho
Type:
Text
Format:
application/pdf
Cataloger:
wbv
Date Digitized:
2012

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Preferred Citation:
"Interacting effects of minimum flow and fluctuating shorelines on benthic stream insects. Research technical completion report, project no. A-052-IDA", Idaho Waters Digital Library, University of Idaho Library Digital Collections, https://www.lib.uidaho.edu/digital/iwdl/items/iwdl-197803.html
Rights
Rights:
Rights to the digital resource are held by the University of Idaho. http://www.uidaho.edu/
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