Dr. David Ahlfeld Professor of Civil and Environmental
Engineering The Westfield River Basin Optimization Model
Demonstration:
Slide 2
KVL CMT BOR LVL WOR WSHP KVL = Knightville (Flood Control) LVL
= Littleville (Flood Control) BOR = Borden Brook (Drinking) CMT =
Cobble Mountain (Drinking/Hydro) WOR = Woronoco (Hydro) WSHP = West
Springfield Hydro Project (Hydro) = Ecological Point of
Interest
Slide 3
Improve current reservoir operations to increase efficiency
Increase hydropower production, increase water supply reliability,
decrease flood risk, etc. Introduce ecological flows to operations
Optimization models will examine how altering operating policies
can improve ecological flows while maintaining or improving current
reservoir objectives Plan for the future (Later Presentation)
Short/long term forecasting and climate change
Slide 4
The optimization model calculates releases on a daily time step
for each reservoir. Releases are the DECISION VARIABLES Storages
are calculated from the Releases: Storage at end of day = Storage
at end of prior day + Inflow during the day Releases during the day
Natural inflows to reservoirs are assumed known.
Slide 5
The model releases are bounded by CONSTRAINTS Example
Constraints: Release Upper Bound Release Through Turbine Turbine
Capacity Reservoir connectivity Assume Reservoir A flows to
Reservoir B Storage of Reservoir B = Prev. Storage at B + Inflows
to B + Outflows from A Releases from B Reservoir Storage Capacity
Reservoir Storage Reservoir Capacity
Slide 6
Example Objective Functions for River Systems: Maximize Income
from Hydropower Generation Maximize Available water for municipal
use Minimize Deviations from a target storage Minimize Deviations
from an ecological flow The optimization model selects releases to
maximize or minimize a given objective THE OBJECTIVE FUNCTION
Slide 7
Targets Can be violated Penalize the objective function as
deviation from the target increases. Example Deviation from Release
Target = Actual Release Target Minimum Release The objective
function minimizes the deviation below the target Constraints
Cannot be violated If the model cannot be satisfy the constraints
the problem is infeasible Example Reservoir Storage 50K acre-ft The
storage must be less than or equal to 50K acre-ft LINGO will report
an infeasible result
Slide 8
Objective Function: Minimize deviations from target storages
for KVL, LVL, and CMT. Minimize deviations from minimum release
targets for KVL and LVL. Minimize flow over flood target point
Maximize power for CMT, WOR, and WSHP Constraints Reservoir
Connectivity (i.e. Storage at WOR = Previous Days Storage +
Releases from KVL, LVL, CMT + Inflow to WOR Releases from WOR)
Reservoir capacities for all reservoirs Turbine capacities for CMT,
WOR, WSHP Ramping and release constraints on reservoir releases
produces more realistic hydrograph (limits the unrealistic release
spikes) The optimization model is solved with LINGO which
communicates with an Excel spreadsheet to read inputs (inflows) and
output the releases and resulting storages.
Slide 9
Minimize = Deviations from Target Storages at LVL and KVL +
Deviations from Target Storages at CMT + Deviations above the Flood
Check Points + Deviations below Min. Flow Targets at LVL and KVL +
Income from CMT power generation + - Income from WOR power
generation + - Income from WSHP power generation + Weight 1* Weight
2* Weight 3* Weight 4* Weight 5* Weight 6* Weight 7* To prioritize
an objective, increase its respective weight. Develop Trade-Off
Curves: Run the model several times, each time changing the
objective function weights.
Slide 10
Begin with analysis of Cobble Mountain (CMT) 70,000 acre-ft
reservoir that supplies water to Springfield. 30.6 MW generating
capacity withdrawals to drinking water facility run through turbine
and any water released back to the river runs through turbine. The
trade-off: How much additional hydropower income can be obtained by
relaxing the reservoirs target volume Vary the weights on CMT
Storage and CMT Hydropower
Slide 11
Each point on the curve represents an operating policy. For
example, this point says if the operations keep the reservoir at
target storage 99% of the time, the income is $1.7M per year Little
increase in income for less reservoir reliability Lets examine this
point
Slide 12
Releases to RiverStorages
Slide 13
Slide 14
The optimization model lets us examine the trade-off between
Cobble Mountain water supply and an instream flow requirement Each
point on the trade-off curve represents the optimal operating
policy for that minimum instream flow.
Slide 15
As expected, it is harder for Cobble Mountain to maintain its
storage target with increasing instream flow requirements
Slide 16
The optimization model will use these 5 reservoirs to hit the
ecological target downstream.
Slide 17
The 2-yr 10-day flow event: The 10 day flow event that is
expected to occur every 2 years. Average flow of 4,500 cfs for 10
days The Best Way Achieve This Flow Event Use the available storage
in the flood control dams to store water for the target. Only use
Cobble Mountain Drinking water if necessary To do this in the
optimization model, heavily weight (or prioritize) CMT target
storage over LVL and KVL. This will use the flood control storage
first.
Slide 18
CMT storage remained constant at each scenario. Drinking water
supply not needed for ecological flow