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 Robert-Bourassa'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-1Phase I Phase II

Mean annual variation of water level : 4,7 m

Mean annual variation of water level : 4,0 m

Mean current : 0,90 m/s Mean current : 1 - 2 m/s

Summer temp.: 8–12 °C

Winter temp.: near 0°C

Summer temp.: 8–14 °C

Winter temp.: 0–0,15 °C

Thin ice cover;(air temperature and discharge)

Many openings

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

22HQme0901

23HQme0901

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