Transcript Impacts Assessment of the Rupert River diversion on Rupert Bay

Impacts Assessment of the Rupert
River diversion on Rupert Bay
Estuary Hydrodynamics
Pierre Dupuis, ing.
Canada
J.Dumas, D.Messier, S.Weyman
7th International Conference on Hydro informatics
HIC 2006 Nice, France
Plan

Eastmain 1A – Rupert river diversion project
– Impacts assessment study required

2D modeling of Rupert Bay hydrodynamics
–
–
–
–
–

Strategy for this study
Data acquisition and analysis
Input to model
Productivity tools used for impact assessments
Results
Conclusion
Eastmain-1-A Project
Province de Québec, Canada
Hudson Bay
La Grande Hydroelectric
Complex
James Bay
Rupert Bay
Eastmain-1-A Powerhouse
Great Lakes
Montréal
Diversion
La Grande 1
La Grande-2-A
Diversion
La Sarcelle
Eastmain-1-A
Rupert Bay
Eastmain-1-A Project






Estimated cost: 2 500 millions €
Added Power : 768 MW + 120 MW
Added Annual Energy: 8,5 TWh
Diversion: 452,6 m3/s mean annual
flow, max: 800 m3/s
Less fresh water inflow in Rupert Bay
In commission: 2011
Objectives and constraints
Rupert Bay hydrodynamics




Get a good understanding of the bay actual
hydrodynamic conditions
Assess the impacts of less freshwater inflow
into the bay
Make sure the study is credible and will be
well received by the public and governmental agencies (federal and provincial)
Proceed according to an established time
frame and within budget!
Rupert bay & Waskaganish
James Bay
17,5 km
Stag Island
Stag Rock
Waskaganish
Cree Native community
Rupert Bay
Waskaganish
Rupert Bay Characteristics





Covers 825 km2
Width of the bay varies from 10 to 18 km
Channel depth varies from 5 to 8 m
Tidal amplitude: 2 m
Salinity of 20-22 ‰ in James Bay
Zones
Maritime
 Mixing
Freshwater


Pontax
Rupert
Broadback
Nottaway
Cabbage Willows – Tidal Flats
Modeling

Numerical modeling is required
– Huge area, low depth, bathymetry

Hydro-Québec chose Mike21™ from DHI (Danish
Hydraulic Institute)
– Accepted within the scientific community
– Well mixed estuary
– Modules HD and AD

Strategy: Simulation of 7 weeks in summer
– Natural conditions
– Post diversion conditions

Simulation of 4 weeks in winter
Required input data



Bathymetry
Downstream boundary tidal signals
Fresh water inflows
Bathymetry


Parallel lines every 200 m
GPS positioning
– Correction for tidal influence
– Crosscheck with perpendicular lines




Vertical precision estimated at 10 cm
Very shallow waters and tidal flats: Airborne
Laser
Took 2 summers to complete work
Cost: 675 000 €
Final result
James Bay
Warm colors: shallow depth
Many channels within the bay
Pontax
Rupert
Broadback
Nottaway
Tidal
gauges

Boundaries
– Mesaconane
– Strutton

Within
– Gushue
Island
– Stag rock
– Rupert river
– Lemoyne
Conditions
aux limites pour
- Marée 1991
Boundary
conditions
for calibration
calibration
- 1991
2 m2
1.5
1 m1
Niveau d'eau [m]
0.5
0 m0
-0.5
-1
-1 m
-1.5
-2 m-2
June 13 1991
July 3
1991-06-13 1991-06-15 1991-06-17 1991-06-19 1991-06-21 1991-06-23 1991-06-25 1991-06-27 1991-06-29 1991-07-01 1991-07-03
00:00
00:00
00:00
00:00
00:00
00:00
00:00
00:00
00:00
00:00
00:00
Date
Iles Strutton
Pointe Mésaconane
Tidal signals
Tidal signal at downstream
Été 2003boundary for modeling
Conditions limites aux frontières aval
3m
3
Super storm of August 22, 2003
2.5
2
0m
Niveau d'eau
1.5
1
0.5
0
-0.5
-1
-1.5
-2 m
-2
2003-08-07
August 7th 2003
2003-08-17
2003-08-27
2003-09-06
2003-09-16
2003-09-26
Date
Pointe Mésaconane
Ile Strutton
2003-10-06
October 20th
2003-10-16
2003-10-26
Fresh water inflow in summer
total: 2500 to 3000 m3/s
(summer 2003)
Débits d'apport - Été 2003
1600
1600 m3/s
Nottaway
1400
1200
Débit m3/s
1000
Rupert natural state
800 m3/s
800
Rupert post diversion
Broadback
600
400
200
Pontax
Nottaway
Broadback
Ruper naturel
Pontax
October 31
Rupert post dérivation
2003-10-31
2003-10-24
2003-10-17
2003-10-10
2003-10-03
2003-09-26
2003-09-19
2003-09-12
2003-09-05
2003-08-29
2003-08-22
August 1
2003-08-15
2003-08-08
0
2003-08-01
0
m3/s
Data acquisition costs (€)





Bathymetry:
Oceanography:
Stations (material & install)
Maintenance (5 years)
Helicopters
Total :
675
640
255
250
250
000
000
000
000
000
€
€
€
€
€
2 070 000 €
Domain


Cell: square 162 m
Grid
– 625 rows
– 370 columns

Chézy coefficient for
calibration
– Tidal range
– Signal deformation


Time step: 90 s
Output: 15 minutes
Calibration

Winter
Summer::35
65
Validation Rupert River
Km 2,5
Km 4,2
Impacts assessment

2 Output files of 15 Gb to work with
– NTFS file system required to store and access
output data
– Special C++ module for retrieving data
– Read directly from binary output files (Mike21
output file of type *.dfs2)
– Can work on matrices (matrix operators)

15Gb was a workable up limit for file size
Tools
Subtractions and
comparisons


Subtracts post
diversion from
natural at any
given time step
Do water level
variation for a given
cell over a given
time period and
compare to field
data – Quick for
validation purposes
Tools
Extrema


Public and policy
makers cannot
always be in front
of the screen
Example:
Maximum speed
modulus for a
five weeks period
for pre and post
diversion
conditions
Tools
Virtual probe



Set start date and
location
Monitors current
speed, depth, time
Helps to:
– understand
circulation patterns
– Zones affected by
each stream
Impact of
diversion


•
•
White: Natural
Black: Post diversion
Less lateral flow
pressure from Rupert
River
Flow from Nottaway
and Broadback will
shift toward the East.
Time of residence
Before diversion
8 days
Start
After diversion
12 days
History of a virtual probe
Before diversion
After diversion
1,4 m/s
Speed
Speed
0 m/s
Azimuth
Travel distance 0-900 km
Duration in days 0-25
Azimuth
Travel Distance 0-1100 km
Duration in days 0-30
Salinity - Modeling





Time step reduced from 90 to 45 s
Salinity was set constant at 20 ‰ at
downstream boundaries
Fresh water threshold : 0,5 ‰
Advection-Dispersion coefficient set to 130
Results showed very good agreement with
measurements at Stag Island and Stag Rock
Fresh water
front



Samples taken
from helicopter
to follow front
For large and
small tides
Used for
calibration
Salinity - Model
Extreme incursion and excursion
From Sept 1st to October 11th 2003
Salinity
Impacts



Translation of the
freshwater front
upstream due to
diversion
Translation estimated to be 4 to 5 km
Waskaganish is still
in the fresh water
zone
Before diversion
Winter - Ice field and flux
Impact at Waskaganish





Imbricated
model
Cell: 54 m
Water levels
Flats (low
tide)
Currents
Conclusion - 1


Study constrained by cost and time schedule
Data requirements to be planned in advance
– Stations carefully located and justifications well explained to
project administrator
– Types of instruments, number of stations, location and
purpose well documented
– Stations maintenance and checkup to be included in costs
– Modeler has to go to the site to get a feel of the system and
must be part of the data gathering team

Real conditions simulated over a long time period are
well received by the public and governmental agencies
Conclusion - 2



Tools are needed to synthesize and
represent results in a suitable form for other
scientists and the public
Interaction between the modeler and
specialists led to development of numerical
tools to address their specific demands
Once created, these tools helped in
producing final results in a short time span
when all field measurements were available
(near the project deadline)
This PowerPoint presentation
can be downloaded from this site in the near future
http:://www.aquapraxis.com/nice2006
Broadback River channel
Salinity
Impact
Différence de salinité [ppm]
Salinité chenal est - Différences pré et post dérivation
3
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
2003-09-02 2003-09-03 2003-09-04 2003-09-05 2003-09-06 2003-09-07 2003-09-08 2003-09-09 2003-09-10 2003-09-11
Date
SE1
SE2
SE3
SE4
SE5
Salinity – Measurements
Stag Rock (moored station)
Depth 4,0 – 6,5 m
Salinity 0 - 4 ‰
Conductivity 0 – 6
Current speed 0,0 – 0,8 m/s
Current direction
Julian day
Impacts - Summer







Fresh water inflow will drop by 20 to 25%
Fluvial circulation will shift toward the north-east
(less pressure from Rupert River)
Residency time in the freshwater zone is one to
two days longer in summer time
Salinity front will translate ≈ 4-5 km southward
Salinity changes from 0,5 ‰ to 1,0 ‰ in the
vicinity of Stag Rock
No perceptible variations within the bay as for
water levels (in terms of mm) and velocity from a
user standpoint
Piston like effect in James bay moves water within
the bay toward the West
Impacts - Winter





Fresh water inflow will drop by 20 %
Time of residence is much longer
Effects from diversion are of lesser importance
Incursion-excursion of fresh water front is within
the limits established for summer
Corroborates the findings of Ingram (1977)
Possible explanation
 System is in a dormant state in winter
– More friction
– Less fresh water inflow
– Tidal amplitudes of lesser magnitude