Transcript Elk Lake: Past and Present

Elk Lake: Past
and Present –
What’s Going
on Inside Elk
Lake
University of Victoria
Environmental Law Centre
29 October 2015
Rick Nordin, British
Columbia Lake Stewardship
Society
Significant Events in the Timeline of
Elk Lake
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Lake formed after retreat of glaciers about 10,000 years ago
European settlement, land clearing, agriculture 1850-1870
Lake impoundment and increased depth and area 1874
Use as drinking water supply for Victoria up to 1914 and to the
Saanich Peninsula until the 1970s
 1950 to present – residential development, 1960 – Pat Bay Hwy
 Popular recreation destination 1920s to present: present
annual use 1.5 million user days, 14,000 angler days, national,
UVic and local rowing facilities
A lake in disequilibrium
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Forest removal in the 1800s
Dam at the outlet raised the lake level 5 m in 1874
Lake volume increased from 7.87 to 18.82 million m3
Lake surface area increased from 141 to 246 ha
Beaver “Lake” pre 1874 very small and surrounded by “swamp”
Pat Bay Highway to service Swartz Bay ferry terminal 1960
Species introductions – fish, bullfrogs, plants and ?
Climate change
Perceived Problems at Elk Lake
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Heavy growth of aquatic plants
Deteriorating water quality – especially cyanobacterial blooms
Loss of fish habitat and fishery productivity
Introduced exotic species
Previous Studies
 Some studies and reports by government agencies (Ministry of Environment,
Fisheries, Saanich, CRD)
 First major water quality study by McKean 1992 (MoE) with WQOs and
recommendation for aeration. Attainment of WQOs poor.
 CRD 1991 recommended a watershed plan
 UVic theses / dissertations Nowlin, Davies, Groeneveld
 Stewardship initiative organized by Golden Rods and Reels 2014
 Water quality review 2014 and assessment of recent data 2015 by Nordin
 Lisa Rodgers MSc thesis
 Restoration options for Elk Lake by Ontario consultant, draft Sept 2015
 New Water Quality Objectives Report by MoE in progress
State of Present Water Quality
 Very dense aquatic plant growth out to about 5 m depth
 Recurring algal blooms which are predominantly cyanobacteria
which pose a serious health risk throughout the year
 Deep water oxygen depletion for most of the year limits the
benthic productivity of the lake (food for fish, habitat for fish)
 Recreational fishing success and satisfaction has declined
(anecdotal)
 Major changes in fish community has altered food chains and
likely affected water quality (opinion)
Elk Lake Basics
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Very small watershed in comparison to lake itself
Consequently very low “flushing rate” (water exchange)
Lake thermally stratifies March through November
Because of thermal stratification, very low and or zero dissolved
oxygen (DO) in the deeper waters of the lake for 6 months of
the year
 The stratification and low DO result in return of phosphorus
from the rich bottom sediments to the water column
 Phosphorus is the key to controlling algal and weed growth
 Most of the phosphorus supply to the lake (85%) is internal load
Lake ecological change
 Initial fish community – 3 species only (Cutthroat Trout,
Brown Bullhead and Prickly Sculpin)
 Present new fish species: Rainbow Trout, Carp, Sunfish,
Perch, LM and SM Bass
 Evidence that there has been major change in the
zooplankton and benthic community
 Aquatic plants have been actively managed for last 50
years – largely by harvesting
 Climate change – increased water temp, longer
stratification period and faster growth of plants
Science Needs
 Much better understanding of fisheries populations – quantification
of species, habitat requirements
 If a whole lake water quality restoration is to be considered
(hypolimnetic aeration or phosphorus binding) considerable
planning and testing needs to be done
 Management of the aquatic plants requires more understanding
and quantification and mapping are essential
 Ongoing monitoring and reporting (nutrients, toxins, DO, coliforms)
and a view to complete ecosystem health assessment
Organizational Needs
 Need for jurisdictional definitions
 Need for co-operation between government agencies
as well as academia and NGOs
 Understanding that are two areas of challenge:
management of aquatic plants and water quality
rehabilitation (phosphorus management)
 Emphasis the absolute importance of Elk Lake – the
ecological, economic and aesthetic value of the lake is
beyond valuation and deserves active management
Thank You!
 Mick Collins, Robert McConnell and GRR
 Michelle Kehler, Deb Epps, (MoE); Scott Silvestri, Neil Goeller
FLNRO
 GRR and Rowing Club samplers (Dennis Gedney, Pat Psaila, Jim
MacDonald, Clive Lane, Brian Williams, David Topham, John Garrett)
 CRD: Laura Kline, Glenn Harris, Dale Green
 Victoria Rowing Society, Rowing Canada, Victoria City Rowing Club,
Brenda Taylor
 Camosun College – Steve Gormican and students
 Intergovernmental Committee (Saanich, CRD, MoE)
 HCTF, FWFSBC, MoE, BCWF, CWF, Victoria F&G Protective Assn,
Peninsula Streams, Colquitz Coalition
 ELC especially Calvin Sandborn