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Report: Trophic state of Elsie Lake Reservoir, 2005 05.As.01
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An assessment of the trophic state of Elsie Lake Reservoir was completed in 2005 as a first step to determine if the reservoir is a candidate for nutrient addition as a measure to restore fish populations. A suite of physical, chemical and biological parameters were examined on a monthly basis from June through October.
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Author: Limnotek Research and Development Inc.,; Perrin, C.J.
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Old Reference Number: 05.As.01
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Old Reference System: FWCP Fish Wildlife Compensation Program - Coastal
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Date Published: Mar 2006
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Report ID: 40914
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Audience: Government and Public
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Elsie Lake Reservoir (Figure 1) is located on Vancouver Island, approximately 40 km northwest of Port Alberni, B.C. The Elsie Lake Dam was constructed in 1957 and became operational in 1959. The main dam impounded the Ash River and it increased the water surface elevation by approximately 18.2 m (312.5 m to 330.7 m). The dam is an earthfill structure that is 30 m high and 189 m long. The impoundment is also supported by four saddle dams located around the northwest end of the reservoir. At full pool elevation, Elsie Lake Reservoir has a surface area of 658 ha, a mean depth of 8 m and a maximum depth of 30 m. The reservoir is approximately 7 km long and 1 km
wide. The reservoir stores up to 84 million cubic meters of water and has a normal drawdown range of 15 m between elevation 331 m and 315.5 m. The reservoir is typically drawn down from July through September and it refills in October through November. The water surface elevation is relatively stable in April through June. The inflows are from 23 streams, but only four have significant year-round flows (Burt and Robert 2003). The catchment area is 218 km2 and the mean annual rate of inflow is 21
m3/sec. Average annual flow of 10.7 m3/s is diverted year-round through a 7.8 km long tunnel and steel penstock to a powerhouse on Great Central Lake that is located south of Elsie Lake Reservoir. The drop in elevation between Elsie Lake Reservoir and the powerhouse is 248 m. The water diversion occurs year round except during a one to two week shutdown for maintenance that is usually scheduled in August of each year (Ash River WUP 2003; Burt and Robert 2003). A minimum flow of 3.5 m3/s is released through a hollow cone valve to support fish habitat in the Ash River downstream of Elsie Lake Reservoir and the average annual water release to the Ash River is 9 m3/s. The Ash River flows south into the Stamp and Somass Rivers, and eventually drains into the Alberni Inlet.
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Report Type
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Fish and Aquatic Habitat Information |
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Subject
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Region - Vancouver Island |
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Fish and Fish Habitat - Impact Assessment |
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Fish and Fish Habitat - Lake |
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Fish and Fish Habitat - Management |
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Watershed Groups - 930 - Vancouver Island (West) Rivers |
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Water Information - Storage Inventory -Lakes and Reservoirs |
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