Lake Diefenbaker Operations

Date
May 30, 2012
Lake Diefenbaker Operations
Context and Objectives
Lake Diefenbaker Statistics
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Lake Diefenbaker
Reservoir Volume at FSL – 9,400,000 dam3
Live Storage – 8,300,000 dam3
Approximate Length – 225 km
Surface Area at FSL – 430 km2
Maximum depth at FSL – 58.5 m
Gardiner Dam
Maximum Height – 64 m
Spillway Capacity at FSL – 6400 m3/s
Qu’Appelle River Dam
Maximum Height – 27 m
Outlet Capacity at FSL – 68 m3/s
Date
Project Purpose
“The project is to provide facilities for the
irrigation of approximately 500,000 acres
of land in Central Saskatchewan and in the
Qu’Appelle Valley and to provide other
benefits to the area including a source of
hydroelectric power, a source of rural and
urban water supply, flood control, and
recreation facilities.”
- Appendix “A”, July 25, 1958 Memorandum of Agreement
Date
Date
Reservoir Uses
• Water Supply from Reservoir
• Irrigation, municipal, industrial, Qu’Appelle Diversion
• Hydropower production
• Reservoir Recreation
• Reservoir Habitat and Fisheries
• Downstream flow regulation
• Water supply – irrigation, municipal
• Transportation, recreation
• Flood protection
• Ecology
Water Supply - Watershed
Image goes here
Water Supply - Runoff
• Unit runoff varies from
10 – 500 dam3/km2
• Volumes are:
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– 20% prairie
– 80% alpine/foothill
– average ≈ 50% snow,
50% rain
• Mean inflow
≈6,600,000 dam3
(AB into SK, 1928-2004)
Water Supply – Alberta Use
• Actual mean inflow
≈ 6,600,000 dam3/yr
≈ 208 m3/s
(AB into SK, 1928-2004)
• If AB was using full
apportionment
≈5,500,000 dam3/yr
State of Supply vs. Use
Median Inflow Year
State of Supply vs. Use
Low Inflow Year (2001 example)
State of Supply vs. Use
High Inflow Year (2005 Example)
Result of Operations
∆ Downstream Flows
∆ Downstream Flows (1969-2011)
Return Period
Without Lake
Diefenbaker (m3/s)
With Lake
Diefenbaker (m3/s)
1:1.4
700
370
1:2
1100
420
1:5
1800
750
1:10
2000
1250
1:20
3000
1800
1:50
3800
1900
1:100
4100
2000
1:500
7700
4200
- Based on Constructed Inflows, 1969-2011
Operating Objectives
Operating Objectives
Operating Objectives
• Safety and Regulatory Constraints
– Passage of the Probable Maximum Flood
– Minimum Operating Level
– E.B. Campbell Minimum Flow
• Operating for Primary Purposes and Co-benefits
– Common operations through fall and winter
– Operations typical for:
• Normal Conditions
• High Flow / Flood Operations
• Low Flow / Drought Operations
Operating Objectives
Operations Challenges
Operations Challenges
Operations Challenges
Date
• Significant decisions must be based on forecasts or even before
precipitation occurs:
– Most basin precipitation occurs after March
• Majority of alpine snow is March and later
• Rainfall is primarily June
– Long term weather forecasts - Insufficient confidence for operating
• Rapid changes in lake levels or outflows are problematic
• Evidence that hydrology is changing
• It is desirable to avoid spill
• Alberta uses continuing toward their 50% entitlement
• Regulatory obligations under SAR and Fisheries can be unclear
• Ad hoc requests for specific outflows
• Must consider North Sask. River flows in operating decisions