Dam Operations Analysis – WW2100
Key Research Questions:
• How well do Willamette reservoirs perform using current
operations under future climate and demographic scenarios?
• What operations strategies, or combination of strategies are the
most robust under future climate and demographic scenarios?
Current reservoir operations: Reservoir
pool elevations are maintained as closely
as possible to the target elevation
(defined by the rule curve – red line in the
figure on the left), given an array of
constraints (minimum and maximum
flows, rates of change, etc..) .
Image: US Army Corps of Engineers – Introducing the rule curve
• How will current dam operations respond
to shifting hydrographs?
• How and when will adjustments to
operations strategies be needed in the
future to satisfy multiple objectives (e.g.
flood control, irrigation, hydropower,
recreation and environmental flows) ?
Overall Analysis Approach:
A. Identify metrics to define system performance in the future
B. Evaluate performance of current operations
a) under future climate change and land use scenarios
b) use results as a baseline to identify shifts in performance metrics
C. Investigate modified operations
a) Identify and evaluate shifted/variable guide curves at major dams to address lack of
performance
D. Examine tradeoffs that arise between competing water uses for each analysis
Model rationale and development to date:
-Modeled reservoir operations based on HEC-ResSim model developed for the
Willamette Basin. Currently, operational information used includes:
1. Rule Curves
2. Operational rules prioritized by zones within reservoir
- Routing and inflow handled by separate Envision plug-ins
- Why not use HEC-ResSim directly?
1. Source code unavailable
2. Flexible description of reservoir operations allows for model transfer to
basins without developed ResSim models in the future
Willamette
Water 2100
Project
A. Reservoir Performance Metrics:
Metric development
–Based on current targets (flow targets from the 2008 Biological Opinion, current control
point channel capacities, etc..)
–Attempt to encompass most relevant management objectives (both today and in future)
Metrics paired to address:
a) The duration of failures: reliability
b) The magnitude of failures: vulnerability
Metrics by relevant management objectives: Flood Control, Environmental Flows, Recreation,
Hydropower, Water Supply
Feedback/Questions about Reservoir Performance
Metrics:
(Please see handouts for details on the formulation of individual performance metrics):
Questions for stakeholders:
•What future management objectives do you anticipate that we're not facing
today?
•How do you feel that the management objectives above should be prioritized
today? In the future?
•How do you see management objectives changing in the future?
•What role do you think the Willamette dams have to play in adaptation to a
changing climate?
B. Evaluation of Current Reservoir Performance:
Analysis Steps:
1.Run the model repeatedly for the future
time period with projected climate and
demand changes to streamflow values
2.Calculate performance metrics at each
reservoir or control point
3. Examine future performance measures
probabilistically
Potential model output format, (adapted from Georgakakos et. al. 2011).
Feedback/Questions about evaluation of current
reservoir performance:
Willamette
Water 2100
Project
C. Investigate Modified Reservoir Operations
1. Perform a sensitivity analysis using
each future landscape trajectory
ƒ Identify high priority reservoirs
(highly sensitive in one scenario or
sensitive in all scenarios) for
operational changes and develop
variable or alternative/ variable rule
curves for only these?
2. Minimize performance failures using each
future landscape trajectory
ƒ Allow releases to vary within a particular
range
ƒ Minimize performance failures at each
time step
ƒ Modeled releases become new rule
curves in future operations scenarios
Variable Rule Curves:
Target pool elevations are variable
based on long range forecasts
updated once or twice monthly.
Feedback/Questions about Modified Reservoir
Operations to consider:
D. Examine Tradeoffs
The impacts of various reservoir operations
scenarios on multiple performance metrics will be
examined side by side, as shown above.
Tradeoffs between two competing
water use metrics can be examined
(weighting by the resource manager
determines position on the pareto
curve shown above).
Feedback/Questions about analysis of tradeoffs:
Question for stakeholders:
What outputs about dam operations performance would be most useful to you for future long
term planning?
References:
Brekke, L.D., E.P. Maurer, J.D. Anderson, M.D. Dettinger, E.S. Townsley, A. Harrison and T.Pruitt (2009), Assessing reservoir operations risk
under climate change, Water Resour. Res, 45, W04411, doi:10.1029/2008Wr006941.
Georgakakos, A.P., et al. Value of adaptive water resources management in Northern California under climatic variability and change:
Reservoir management. J. Hydrol. (2011), doi:10.1016/j.jhydrol.2011.04.038
Willamette
Water 2100
Project