Transcript Environmental Monitoring of La Grande-2-A and La Grande-1 Projects

Environmental Monitoring of La
Grande-2-A and La Grande-1
Projects
Danielle Messier
McGill University, 2003-09-25
La Grande Complex
Context of the monitoring
• Required by the certificates of
authorization of projects constructed
during phase II of the La Grande Complex
• Section 22 of the James Bay and Northern
Québec Agreement (1975)
The projects on the Grande Rivière
• Addition of La
Grande-2A
underground
generating station
beside RobertBourassa's (PK 112)
• Construction of La
Grande-1 run-of-river
generating station
(PK 37)
Sources of modifications
• Increase of the designed flow from
4300 m3/s to 5920 m3/s
– Changes in the production pattern: increase
flow in winter time, decrease in summer time
• Creation of La Grande-1 reservoir
– Area of 70 km2
• Operation of La Grande-1 generating
station
Objectives of the monitoring
• To verify the actual modifications of the
environment following impact assessment
study
• To detect unpredicted impacts and take
action to avoid or mitigate them
• To enhance impact assessment and
mitigation measures
Criteria used for the monitoring
• Components of the monitoring program
must reflect the changes
• Changes must be measurable
• Methods must be accepted
• Changes must be beyond natural
variability
Components of the monitoring
• Hydrology
– discharge, water level,
temperature, current
• Erosion of river banks
• Water quality
• Riparian and aquatic
vegetation
• Fish
• Mercury in fish
• Underice freshwater
plume
• Eelgrass
Main periods of the monitoring
• Reference period :
1985-1990
• Transitory period :
1991-1992
• Monitoring period :
1992-2000
Modifications of the discharge
Hydraulic Modifications
downstream from La Grande-1
Phase I
Mean annual variation of
water level : 4,7 m
Mean current : 0,90 m/s
Phase II
Mean annual variation of
water level : 4,0 m
Mean current : 1 - 2 m/s
Summer temp.: 8–12 °C Summer temp.: 8–14 °C
Winter temp.: near 0°C Winter temp.: 0–0,15 °C
Thin ice cover;
Many openings
(air temperature and
discharge)
River banks erosion
Transitory : 1991-1993
Exploitation : 1997-1999
Upstream LG-1:
500 000 m3 material
eroded
Upstream LG-1
200 000 m3 material
eroded
Downstream LG-1:
100 000 m3 material
eroded
Downstream LG-1:
75 000 m3
Construction of
protection structures
River banks erosion
• The Grande Rivière is
enlarging to adapt to
increased mean
annual discharge
• 3 large landslides
occurred :
– 3.5 M m3 in 1987
– 1.5 M m3 in 1989
– > 1 M m3 in 2003
Fish Communities
• Few changes in the
fish communities of
La Grande-1 reservoir
and estuary
• No transfer of fish
between Grande
Rivière and other
tributaries of James
Bay
Mercury in fish
• Impoundment of La
Grande-1 reservoir
did not change
mercury
concentrations in fish
• The effect of the
Grande Rivière on
James Bay fish is
restricted to the
summer plume area
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The freshwater underice plume
• Increasing the
discharge from 1700
m3/s to more than
4400 m3/s extends
the plume area from
1600 km2 to 2100 km2
or 3500 km2,
depending on ice
conditions
The La Grande plume in 1995
Eelgrass in James Bay
• General distribution of
eelgrass beds in
James Bay shows
high stability from
1986-87 up to 1996
• Massive decline in
1998-1999 along
James and Hudson
Bays, due to wasting
disease
Production of eelgrass
• Data from 1988 to 2000
• High annual variation at
all stations and all depths
• Meterological conditions
are responsible for
annual variations
• Isostatic uplift causes
long term disappearance
in shallow waters
Variation in eelgrass production
Variation in salt marshes
• 10 permanent
stations from 1991 to
1999
• Vegetation changes
under isostatic uplift
• Noticeable expanses
of vegetation
Changes in salt marshes
Conclusions
• Most environmental changes in the
Grande Rivière were observed during
phase I
• Commissioning of La Grande-2A and La
Grande-1 generating stations did not
generate cumulative effects
• The main changes are direct hydrological
conditions, including the increase of the
freshwater underice plume