GoldSim Regional Water Supply Model:
Seattle System
Landsburg Diversion Dam
Source: Seattle Public Utilities. “Cedar River Watershed Virtual Tour.”
http://www2.cityofseattle.net/util/tours/CedarRiverTour/slide3a.htm
University of Washington
Water Resources Management and Drought Planning Group
September 15, 2006
Seattle Supply System
2
Table of Contents
GoldSim Regional Water Supply Model: Seattle System ............................................................. 1
Table of Contents ........................................................................................................................... 2
List of Figures ................................................................................................................................ 3
List of Tables .................................................................................................................................. 3
Introduction.................................................................................................................................... 4
Introduction.................................................................................................................................... 4
Supply System Background ........................................................................................................... 4
Model Purpose................................................................................................................................ 5
Model Methodology........................................................................................................................ 6
Firm Yield ............................................................................................................................................... 6
Study Period ............................................................................................................................................ 6
Time Step ................................................................................................................................................. 7
Conjunctive Use Operating Rules ......................................................................................................... 8
Modeled System Description .......................................................................................................... 8
Cedar River System ................................................................................................................................ 8
Cedar Reservoir....................................................................................................................................................9
Cedar Dead Storage Alternative ......................................................................................................................... 11
Cedar Reservoir Rule Curve .............................................................................................................................. 11
Natural Outflow & Reservoir Releases .............................................................................................................. 12
Cedar River Minimum Instream Flows (MIF’s) ................................................................................................ 14
South Fork Tolt River System ............................................................................................................. 15
South Fork Tolt Reservoir .................................................................................................................................. 16
Tolt Reservoir Rule Curve ................................................................................................................................. 17
Reservoir Releases ............................................................................................................................................. 18
South Fork Tolt River Instream Flows ............................................................................................................... 18
Seattle Well Fields ................................................................................................................................ 19
Municipal and Industrial (M&I) Demands ........................................................................................ 20
Running the Model ...................................................................................................................... 20
Introduction and Navigation ............................................................................................................... 21
Model Settings ....................................................................................................................................... 21
Input Controls ....................................................................................................................................... 22
Cedar Reservoir Controls ................................................................................................................................... 23
Tolt Reservoir Controls ...................................................................................................................................... 24
Supplemental Supplies ....................................................................................................................................... 25
Demand Controls ............................................................................................................................................... 27
Run Controller ...................................................................................................................................... 28
System Outputs ..................................................................................................................................... 29
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Reservoir Storages ............................................................................................................................................. 29
Minimum Instream Flows .................................................................................................................................. 30
Municipal and Industrial Demand ...................................................................................................................... 31
Additional Resources............................................................................................................................ 32
Contact.......................................................................................................................................... 32
Sources ......................................................................................................................................... 32
Figure Sources ............................................................................................................................. 33
Appendix A: Seattle Regional Water Supply System .................................................................. 35
Appendix B: Inflow Locations..................................................................................................... 36
Appendix C: Cedar Minimum Instream Flow Requirements and Rule Curve ......................... 37
Appendix D: Tolt Minimum Instream Flow Requirements and Rule Curve ............................ 38
Appendix E. Sample GoldSim Dashboard ................................................................................. 39
Appendix F: Seattle Water Supply Model Default Input Values ............................................... 40
List of Figures
FIGURE 1. WOODSTAVE PIPE INSTALLED TO CARRY CEDAR RIVER WATER TO SEATTLE, 1899.......................................5
FIGURE 2. CEDAR RIVER SYSTEM...................................................................................................................................9
FIGURE 3. MASONRY POOL .......................................................................................................................................... 10
FIGURE 4. CEDAR RESERVOIR ELEVATIONS ................................................................................................................. 10
FIGURE 5. CEDAR RESERVOIR DEFAULT RULE CURVE ................................................................................................. 12
FIGURE 6. CEDAR MORAINE ......................................................................................................................................... 13
FIGURE 7. CEDAR RIVER .............................................................................................................................................. 14
FIGURE 8. CEDAR RIVER MINIMUM INSTREAM FLOW REQUIREMENTS ........................................................................ 15
FIGURE 9. SOUTH FORK TOLT RIVER SYSTEM ............................................................................................................. 16
FIGURE 11. TOLT RULE CURVE ................................................................................................................................... 17
FIGURE 10: TOLT RESERVOIR ....................................................................................................................................... 17
FIGURE 12. TOLT TREATMENT FACILITY ...................................................................................................................... 18
FIGURE 13. SOUTH FORK TOLT RIVER MINIMUM INSTREAM FLOW REQUIREMENTS.................................................... 19
FIGURE 14. AQUIFER STORAGE AND RECOVERY SYSTEM ............................................................................................ 19
FIGURE 15. SEATTLE MODEL INTERFACE MAIN PAGE ................................................................................................. 21
FIGURE 16. MODEL SETTINGS WINDOW ....................................................................................................................... 22
FIGURE 17. CEDAR RESERVOIR INPUT CONTROLS ........................................................................................................ 23
FIGURE 18. TOLT RESERVOIR INPUT CONTROLS .......................................................................................................... 24
FIGURE 19. SUPPLEMENTAL SUPPLY INPUT CONTROLS ................................................................................................ 25
FIGURE 20. DEMAND INPUT CONTROLS........................................................................................................................ 27
FIGURE 21. RUN CONTROLLER .................................................................................................................................... 28
FIGURE 22. UPPER-MOST LEVEL OF THE SEATTLE WATER SUPPLY SYSTEM MODEL................................................... 28
FIGURE 23. CEDAR RESERVOIR STORAGES................................................................................................................... 29
FIGURE 24. MINIMUM INSTREAM FLOW OUTPUT STATISTICS ...................................................................................... 30
FIGURE 25. MUNICIPAL AND INDUSTRIAL DEMAND OUTPUT STATISTICS .................................................................... 31
List of Tables
TABLE 1. MONTH NUMBERING ......................................................................................................................................7
TABLE 2. CEDAR RESERVOIR OUTFLOWS ..................................................................................................................... 13
TABLE 3. MUNICIPAL AND INDUSTRIAL MONTHLY DEMAND FACTORS ....................................................................... 20
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Introduction
In 2006, King County initiated a partnership with the University of Washington (UW) to forecast
future regional water demand, including the impacts of population and climate. As a product of
this collaboration, a set of dynamic water supply models have been created to explore these
issues. The models were designed with methodologies and assumptions that reflect those
incorporated in the supply models currently in use by Seattle Public Utilities (SPU), Snohomish
County Public Utility District (SnoPUD), and Tacoma Water. This report contains a detailed
description of one of these models, the Seattle Water Supply System Model.
The report first provides a brief background on the development of the Seattle water
supply system’s three supply sources: the Cedar River water system, the Tolt River water
system, and the Seattle Well Fields. The paper then presents the current supply system structure,
as well as a description of how the system is modeled. Finally, this documentation introduces
the user to the operation of the Seattle Water Supply System Model using the model’s interface.
Supply System Background
Towards the end of the 19th century, rapid population growth lead the City of Seattle to consider
the development of a municipal water system as an alternative to the wells, springs, and private
companies that supplied water. On June 6, 1889, before the suggestion could be considered, the
"Great Seattle Fire" destroyed much of Seattle, including the 64-acre business district. The city's
response was largely hindered by its patchwork supply system, which exacerbated the extent of
the damage. When Mayor Robert Moran officially proposed that the city develop its own
municipal water system, the vote showed resounding approval: 1,875 to 51.
In 1890, Seattle issued $845,000 in bonds in order to buy the Spring Hill Water Company
and the Union Water Company. With this purchase, the primary supply sources for the new
municipal system became Lake Union and Lake Washington.
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In 1895, the city began developing the Cedar
River water system, which became operational in
1901 (Figure 1). The Volunteer Park and Lincoln
reservoirs were then constructed on Capitol Hill as
storage basins for the city. The Cedar River water
was diverted by a dam at Landsburg and transported
through a 28.6 mile pipeline to these reservoirs.
Though the system had a capacity of 23.5 million
gallons per day, Seattle was experiencing rapid
growth. In 1909, a second pipeline was installed that
supplied an additional 45 million gallons per day.
The system was again expanded in 1964 when
the South Fork of the Tolt River was developed as a
Figure 1. Woodstave pipe installed to carry
Cedar River water to Seattle, 1899
supply source. Later expansion occurred in 1987,
when two wells in the Highline Well Field (now the
Seattle Well Fields) became operational, and again when a third was added in 1990.
Today, the Seattle water supply system serves approximately 1,350,000 people. With
630,000 retail customers, less than half of the supplied population resides in the City of Seattle.
The remaining 720,000 people live in the surrounding area and purchase their water wholesale.
The system is managed by Seattle Public Utilities (SPU), which was formed in 1997 as a result
of the consolidation of the Seattle Water Department with other city agencies. (See Appendix A
for a map of the current Seattle water supply system.)
Model Purpose
The primary purposes of the Seattle Water Supply System Model are to explore infrastructure
development options, alternative operating procedures, and the potential impacts of climate
change. The results from demand forecast models and regional streamflow forecasting systems
can be incorporated to produce a comprehensive evaluation of future supply system alternatives.
Such analyses will prove vital to decision makers as they manage the Seattle water supply
system to meet the city’s various urban, environmental, and recreational water demands well into
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the future. To this end, the model was designed to be easily modified and expandable, with the
expectation that it will continue to be a valuable tool, even as system conditions change.
Model Methodology
Seattle Public Utilities’ Water Management Section currently uses a Conjunctive Use Evaluation
(CUE) model in its management of the system. The CUE model was developed with
programming software STELLA, from High Performance Systems. The methodology,
assumptions, and operating rules of the 2006 CUE model were incorporated into the University
of Washington’s model, which was constructed using GoldSim Technology Group’s GoldSim
Simulation Software. The advantages of this software over the STELLA program include, but
are not limited to:

An internal calendar

Easy interface development

Automated unit analysis

The ability to link separate models

Graphically oriented programming
Firm Yield
The goal of the Seattle Water Supply Model is to determine the reliability of the Seattle Water
Supply system given scenarios featuring alternative management practices, supply sources, and
future climate scenarios. SPU has set a 98% reliability standard, such that the firm yield is the
annual rate (reported in million gallons per day) at which water can be consistently delivered in
all but the driest 2% of years. Supplied with historic inflow data as input, the model simulates
the system given the physical constraints of the storage, transmission, and treatment systems, as
well as user-specified operating rules. In the event that the reliability standard is not met, the
supply system is deemed inadequate for the specified conditions.
Study Period
The Seattle Water Supply System Model currently operates with weekly inflow data available
from October 1, 1928 to September 30, 2003. Hydrosphere Consultants generated the original
inflow dataset for SPU in 1994, and since that time it has been regularly updated by SPU. In
order to meet the 98% reliability standard, the modeled Seattle System can fail twice in 100
years, or once in 50 years. In its own simulations, SPU operates the CUE model with the
constraint that a maximum of one failure is allowable for its 76-year record (SPU has
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incorporated data up to 2004). Alternative data sets representing potential future flows can also
be incorporated into the Seattle Water System Supply Model.
Time Step
In contrast to SPU’s CUE model, the Seattle model runs on a daily rather than weekly time step.
Advances in computer processing ability and advantages of the GoldSim software, such as its
internal calendar and automated unit analysis, make this possible without significant drawbacks.
Use of a daily time step eliminates the need for an 8 or 9 day week at the end of each water year,
as is found in the CUE model. It also reduces the likelihood of overestimating water supplies
available from run-of-river sources, which is a drawback of the weekly time step.
Daily, weekly, and monthly operating rules are easily applied via GoldSim’s convenient
numbering system. However, it should be noted that GoldSim denotes January 1st, the beginning
of the calendar year, as the first day and month of a year. This contrasts the traditional modeling
technique of using October 1st, the beginning of the water year, as the first day and month of a
year (Table 1).
Table 1. Month Numbering
GoldSim
(Calendar
Year Month)
January
February
March
April
May
June
July
August
September
October
November
December
Assigned
Number
1
2
3
4
5
6
7
8
9
10
11
12
Stella
(Water Year
Month)
October
November
December
January
February
March
April
May
June
July
August
September
Additional information regarding time and time steps can be found below in the
“Running the Model/Model Settings” section.
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Conjunctive Use Operating Rules
Seattle Public Utilities conjunctively manages the timing and volume of deliveries from each of
its three storage sources: the Cedar Reservoir, Tolt Reservoir, and Seattle Well Fields.
According to SPU, “Conjunctive use refers to the combined use of multiple water supply sources
to optimize resource use and minimize adverse effects of using a single source” (2007 Water
System Plan, pp. 2-5). Supply sources are generally managed according to a specific set of
operating rules that define the order in which supplies are used.
Prior to any other withdrawals, the Seattle Well Fields are assumed to supply 10 mgd.
However, they are only operational during the peak season—after July 1st and before December
1st—and for no longer than 14 consecutive weeks.
Run-of-river flows downstream of the reservoir are not available in the South Fork Tolt
River. However, natural inflows to the Cedar River between the Masonry Dam and Landsburg
Diversion (Cedar 2; See Appendix B for complete list of inflow names and locations) can be
used to meet municipal and industrial (M&I) demands once instream flows have been met.
Lastly, the storage in the two reservoirs is used to meet demands. Both the Cedar and
Tolt Reservoirs must meet a specific minimum delivery due to the physical limitations of the
distribution system. The minimum service requirements are 30% and 25% of the system’s final
demands (M&I demands, firm supply, and highline recharge requirements) for the Cedar
Reservoir and Tolt Reservoir, respectively.
If one of the two reservoirs is full, but the other is not, then demands are met by the full
reservoir (excepting the minimum delivery provided by the reservoir that is not full). When this
is not the case, releases are determined based on the amount of water each reservoir has available
for use. Available water consists of the reservoir storage and current inflows, minus current
evaporation, seepage, and instream flow requirements.
Modeled System Description
Cedar River System
The Cedar River provides approximately 70% of Seattle’s M&I supplies, making it the primary
source of water for the Seattle Water Supply System. Part of the Cedar River Municipal
Watershed, the Cedar River originates on the west side of the Cascade Range in southeast King
County, and flows northwest towards Seattle (Figure 2). The Seattle Water Supply System
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Model utilizes data from six inflow locations on the Cedar River; two sites are upstream of the
primary storage reservoir, while the remaining four are downstream (Appendix B).
Figure 2. Cedar River System
Cedar Reservoir
The Cedar Reservoir operates in a rather complicated hydrological environment. The principal
storage for the Cedar River is Chester Morse Lake. The lake is formed by an overflow dike that
has an elevation of 1546 ft. Flashboards increase the crest of the overflow dike to 1550 ft.
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Chester Morse Lake is a portion of the
masonry pool that is formed by the Masonry
Dam, (Figure 3). When the masonry pool
storage surpasses the crest of the overflow
dike, the two water bodies merge and
behave as a single reservoir. The combined
Cedar Reservoir (Figure 4) has a maximum
storage elevation of 1570 ft. The 1,680 acre
Cedar Reservoir has a capacity of 15.8
Figure 3. Masonry Pool
billion gallons (48,500 AF) above its natural
gravity outlet.
Modeled as two reservoirs, this system is complicated in that seepage occurs between the
overflow dike and Masonry Dam. A majority of this water recharges the Cedar River, while the
remainder is lost through other outlets.
The current dead storage elevation at Chester Morse Lake is 1532 ft (36,064 AF). Water
below this elevation is not available for use via gravity flow. While the normal minimum
operating level of the masonry pool is 1530 ft, it can be further reduced to 1510 ft (415 AF) in
order to minimize seepage during dry periods.
Figure 4. Cedar Reservoir Elevations
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Cedar Dead Storage Alternative
The active storage capacity of the Cedar Reservoir can be increased if a pumping alternative is
implemented. Two sets of barge-mounted pumps are stored on the lake year-round, and each has
a capacity of 120 mgd. These pumps can be anchored near the outlet in emergency situations in
order to access water stored near lake-bottom, an elevation of 1502 ft. This is 30 ft below the
gravity outlet, and increases the available water supply by 11.1 billion gallons (34,050 AF).
Pumps have been used historically to help mitigate drought conditions, and may be used more
regularly in the future.
Cedar Reservoir Rule Curve
A reservoir rule curve indicates target storage volumes throughout the year. For SPU’s system,
these curves typically establish the maximum volume of water that can be stored for a given
reservoir, for a specific time of year. The default rule curve (Figure 5) for the Cedar Reservoir
sets the maximum fill elevation of the reservoir at 1560 ft (84,565 AF). During the third week of
August system operators prepare for the fall flood season by releasing water. The Cedar
Reservoir is then drawn down to 1550 ft (65,647 AF) by October 1st, the beginning of the water
year. This is the maximum storage volume held throughout the winter months. Between the
third week of February and the first week of May, the reservoir is gradually refilled to the
maximum 1560 ft (84,565 AF). (See Appendix C for a table of weekly rule curve values.)
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Cedar Rule Curve
(1560ft Max.)
90000
Rule Curve
Dead Storage w /o Pumping
Dead Storage w / Pumping
Storage Volume (af)
80000
70000
60000
50000
40000
30000
20000
10000
1-Sep
1-Aug
1-Jul
1-Jun
1-May
1-Apr
1-Mar
1-Feb
1-Jan
1-Dec
1-Nov
1-Oct
0
Date of Year
Figure 5. Cedar Reservoir Default Rule Curve
While these default values are used as operating guidelines, with close monitoring the
Cedar Reservoir can actually be operated to store water to 1563 ft, and it can store flood waters
to a maximum of 1570 ft. As such, in addition to the default rule curve, three alternative curves
are available in the model. Two of these are similar to the default curve, except that their
maximum (summer) storage levels are 1562 ft (88,460 AF) and 1563 ft (90,449 AF)
respectively. The third alternative is a curve with a constant elevation value of 1590 ft (154,800
AF), a scenario that can be used to surcharge the system.
Natural Outflow & Reservoir Releases
Water leaves the Cedar Reservoir through six paths (Table 2). The first path is natural seepage
outflow. North of the masonry pool and between the Masonry Dam and overflow dike is a
moraine aquifer (Figure 6) fed by seepage from the masonry pool. Both aquifer storage and the
masonry pool water level dictate the rate of seepage. While the majority of the seeped water
recharges the Cedar River between the Masonry Dam and Landsburg, some leaves the system
via the Snoqualmie River Basin.
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Figure 6. Cedar Moraine
Controlled flows can be released from the Cedar Reservoir to the Cedar River in five
ways. The majority of water is released through two penstocks (pipes) that lead to Seattle City
Light’s Cedar Falls Hydropower Plant. The powerhouse has a maximum capacity of 750 cfs,
and the utilized flows are returned to the Cedar River downstream of the Masonry Dam.
Alternatively, up to 650 cfs can be released through a spill valve at the Masonry Dam. In
addition, depending on the masonry pool level, up to 45 cfs can be released via the Masonry
Dam’s stream flow valve. When open (October through March), a Masonry Dam service
spillway gate with a 1557 ft crest can release 4400 cfs (the 100-year flood) when the masonry
pool is at 1570 ft. During flood events, an emergency spillway gate at the Masonry Dam with a
1543 ft crest can release the 70,000 cfs when the masonry pool is at 1570 ft.
Table 2. Cedar Reservoir Outflows
Cedar Reservoir Outflow Options
Masonry pool seepage
Hydropower plant penstocks
Masonry Dam spill valve
Masonry Dam stream flow valve
Masonry Dam service spillway
Masonry Dam emergency spill
Maximum
Capacity
NA
750 cfs
650 cfs
28 cfs to 45 cfs
4,400 cfs
70,000 cfs
Operation Notes
Function of aquifer storage and masonry
pool water level
Flows returned to Cedar River 2 miles
downstream of Masonry Dam
Reservoir spill
Depends on masonry pool water level
Fully open October through March
Operated only during flood events
Fourteen miles downstream, at the Landsburg Diversion Dam and fish passage facility,
some of the Cedar River water is diverted to Lake Youngs. Lake Young’s is used primarily as a
regulation pool and its storage volume is not generally considered when determining firm yield
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unless the user activates the Lake Youngs Drawdown alternative in the model. Flows travel
from the diversion dam to Lake Youngs via Landsburg Tunnel, which has a maximum capacity
of 277 mgd. Upon leaving the Cedar Treatment Facility at Lake Youngs, water enters the
southern portion of the SPU service area.
Cedar River Minimum Instream Flows (MIF’s)
For the purposes of habitat
preservation, instream flows on the
Cedar River (Figure 7) must meet a
certain minimum that varies
throughout the year. The MIF
values were specified in the Cedar
River Habitat Conservation Plan
(HCP) Instream Flow Agreement
(IFA) (2000). The HCP/IFA
stipulates that 30 cfs be supplied
year-round above the Cedar Falls
Figure 7. Cedar River
Hydropower Plant, at USGS station
No. 12116400. This volume is released in the process of meeting downstream flow requirements
at Landsburg’s USGS station No. 12117600. As such, only the downstream MIF needs are
modeled.
The HCP/IFA specifies not only minimum instream flow requirements during normal
periods, but also critical flow criteria, critical period MIF’s, and several supplemental instream
flow blocks that are to be supplied less frequently. However, because there are no precise
triggers established for these supplemental blocks, they are not applied in the model. Below is a
chart (Figure 8) showing the normal and critical minimum instream flow requirements
throughout the year, and a detailed table can be found in Appendix C.
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Cedar River Instream Flow Requirements
(Landsburg)
300
Flowrate (cfs)
250
200
150
100
50
1-Sep
1-Aug
1-Jul
1-Jun
1-May
1-Apr
1-Mar
1-Feb
1-Jan
1-Dec
1-Nov
1-Oct
0
Date of Water Year
Figure 8. Cedar River Minimum Instream Flow Requirements
South Fork Tolt River System
The South Fork Tolt River supplies approximately 30% of Seattle’s municipal water needs,
primarily serving the northern and eastern region of the SPU service area. It is located in the
South Fork Tolt River Municipal Watershed, approximately 13 miles east of Duvall in King
County (Figure 9). Inflows to the system are monitored at three locations: Tolt 8 (USGS gage
12148000), Tolt 20 (calculated based on river basin characteristics), and Tolt 7 (USGS gage
12147600). Tolt 7 represents headwater flows near Index, while Tolt 20 consists of local inflows
to the Tolt Reservoir, the primary storage facility for the South Fork Tolt River System. Tolt 8
represents all inflows to the South Fork Tolt River between the Tolt Reservoir and Carnation,
where minimum instream flow requirements must be met.
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Figure 9. South Fork Tolt River System
South Fork Tolt Reservoir
The South Fork Tolt Reservoir (Figure 10) currently has a maximum active storage capacity of
13.7 billion gallons (42,155 AF). Water can be stored to a maximum elevation of 1765 ft, when
the ring gate is in place (March – August). Current minimum operating elevation is 1710 ft
(15,745 AF) in order to limit turbidity levels.
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Tolt Reservoir Rule Curve
Unlike the Cedar system, modeling of the Tolt
Reservoir is limited to one rule (Figure 10: Tolt
Reservoir). A two-phase drawdown of the Tolt
Reservoir begins during the last week of
August, such that the storage volume in the Tolt
Reservoir is 48,800 AF on October 1st, to begin
the water year. This is the maximum volume of
water retained throughout the winter months,
until the refill period begins during the last week
Figure 10: Tolt Reservoir
of January. In the first stage of refill, the
reservoir is filled to 56,100 AF (1762 ft) by the second week in February, and this level is
maintained for three weeks. During the second phase, a ring gate is raised to increase the storage
volume to its maximum of 57,900 AF (1765 ft). The additional 1,800 AF is filled by the second
week in March, followed by drawdown, again, in late August. (See Appendix D for a table of
weekly rule curve values.)
Tolt Rule Curve
(Dead Storage: 1710ft)
70000
Rule Curve
Dead Storage (1710ft)
Storage Volume (af)
60000
50000
40000
30000
20000
10000
1-Sep
1-Aug
1-Jul
1-Jun
1-May
1-Apr
1-Mar
1-Feb
1-Jan
1-Dec
1-Nov
1-Oct
0
Date of Year
Figure 11. Tolt Rule Curve
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Reservoir Releases
Water can be released from the South
Fork Tolt Reservoir to the South Fork
Tolt River via a spill valve, a morning
glory spillway, or the hydropower
plant’s river return structure. The water
is then delivered to a regulating basin as
a precursor to being processed by the
Tolt Treatment Facility (Figure 12).
Historically, the South Fork Tolt
Figure 12. Tolt Treatment Facility
River has provided high quality drinking
water and required minimal treatment. However, events featuring low reservoir levels, high
winds, and heavy rains lead to turbidity levels well over the 5 nepha turbidity unit (NTU) limit
for unfiltered water sources. To allow for continuous operation during these high turbidity
flows, the Tolt Treatment Facility (TTF) was constructed. A public-private partnership project
between SPU and Azurix CDM, the facility became operational in 2000. While the regulating
basin can potentially deliver water to the Tolt Treatment Facility at a maximum rate of 135 mgd,
the Tolt Treatment Facility has a limited capacity of 120 mgd.
South Fork Tolt River Instream Flows
As a part of the Federal Energy Regulator Commission (FERC) licensing process for the
hydropower plant, minimum instream flows were specified in the 1988 South Fork Tolt River
Hydroelectric Project Settlement Agreement. The agreement specifies normal and critical
minimum instream flows as well as critical flow criteria. Minimum instream flows of 20 to 30
cfs are required immediately below the South Fork Tolt Dam, and are easily achieved in the
process of meeting the more variable downstream flow requirements at Carnation (USGS gage
12148000). Specific values for the minimum instream flows (Figure 13) can be found in
Appendix D.
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Tolt Instream Flow Requirements
80.00
Normal
Critical
Flowrate (cfs)
70.00
60.00
50.00
40.00
30.00
20.00
10.00
9/1/06
8/1/06
7/1/06
6/1/06
5/1/06
4/1/06
3/1/06
2/1/06
1/1/06
12/1/05
11/1/05
10/1/05
0.00
Date of Year
Figure 13. South Fork Tolt River Minimum Instream Flow Requirements
Seattle Well Fields
The Seattle Well Fields (formerly the Highline Well Fields) provide approximately 1% of
Seattle’s municipal and industrial water supply, and, when operational, is drafted before
reservoir storage. The three wells are located just north of Seattle-Tacoma International Airport,
with two at the Riverton Well Field and one
at the Boulevard Park Well Field (see
Appendix A).
The wells are generally used to
supplement supply during the peak season,
when they are pumped continuously for 14
weeks. The well supply becomes available
on July 1st of each calendar year, and
pumping begins when the Cedar Reservoir
Figure 14. Aquifer Storage and Recovery System
releases water to meet M&I demands. The
current maximum pump rate is 10 mgd, but this value can be adjusted by the user to investigate
other alternatives. While the wells are naturally recharged, they can also be artificially recharged
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
20
at a rate of 5 mgd. This is accomplished using a method called aquifer storage and recovery
(ASR) (Figure 14) and makes use of treated water from the Cedar River distribution system.
Municipal and Industrial (M&I) Demands
Municipal and industrial demands are calculated as a portion of an annual average base demand.
Monthly demand factors (Table 3) have been determined based on historical data (1994 - 2000)
and are assumed to apply under average weather conditions. For a given month, the modeled
M&I demand is equal to the product of that month’s demand factor and the specified base
demand (currently 171 mgd).
Table 3. Municipal and Industrial Monthly Demand Factors
Month of
Year
January
February
March
April
May
June
July
August
September
October
November
December
Monthly
Demand
Factor
0.85
0.85
0.86
0.88
0.98
1.13
1.34
1.35
1.12
0.93
0.86
0.85
Running the Model
The GoldSim Player software used to run simulations can be downloaded for free from the
GoldSim website (http://www.goldsim.com/Form_DownloadPlayer.asp). Once the software is
installed, the GoldSim Player file for the model (Seattle_Supply_System.gsp) can be operated.
To run simulations, the model requires that the three Microsoft Excel files
(Cedar_Reservoir_Daily.xls, Tolt_Reservoir_Daily.xls, and SPU_Flows_Daily.xls), that contain
input data used in the model, be placed in the same folder. These files can all be obtained by
contacting the Water Resources Management and Drought Planning Group at the University of
Washington (see Contact section).
Once the GoldSim Player software is installed, and the Seattle player file and
corresponding data files are placed in the same folder, open GoldSim Player. A menu appears,
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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and the “Open File” button is selected. Then, locate and select the Seattle player file
(Seattle_Supply_System.gsp). The Seattle player file consists of several user-interface
dashboards that compose the system interface. The dashboards are designed for ease of use, so
that navigating the model, changing simulation settings, running simulations, and viewing results
are simple processes. The model should open to the main dashboard screen, “Seattle Water
Supply System,” shown and described below (Figure 15).
Introduction and Navigation
The Seattle main page provides users a
brief introduction to the Seattle Water
Supply System Model. The user
employs the toolbar at the bottom of the
main page (see Appendix E) to navigate
to any of the four input pages: Cedar
Reservoir, Tolt Reservoir, Demands, and
Supply Supplements. Alternatively, the
model can be run directly from the main
page via the “Run Controller” in the
center of the lower toolbar. Output can
Figure 15. Seattle Model Interface Main Page
be viewed by clicking any of the desired
system output buttons located on the right side of the toolbar. This toolbar is included on all of
the Seattle Water Supply System Model interface pages and is the primary means of navigating
and operating the model. The system inputs, system outputs, and run controller are each
discussed in further detail below.
Unique to the interface main page is a “System Background” toolbar that runs along the
right side of the page. It is highly recommended that new model users explore the four options
presented by the toolbar: Model Settings, History, System Map, and System Description.
Model Settings
The Seattle Water Supply System Model time settings can be easily adjusted. This is
accomplished by navigating to the main interface page (Seattle Water Supply System) or any of
the system background pages, and clicking the “Model Settings” button located in the toolbar
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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along the right side of the page. A small dialogue
box (Figure 16) appears that allows the user to adjust
the time counters’ units, as well as the actual period
of analysis. Users should specify the simulation start
and end dates (within the range of Oct. 1, 1928 and
Sept. 30, 2003) to adjust the study period as desired.
The “duration” option should not be used to change
the study period, as this will alter the way that the
model tracks time during a simulation.
In addition, basic information regarding the
model structure can also be accessed by clicking on
Figure 16. Model Settings Window
the “Information” tab at the top of the model settings
window. The Monte Carlo tab can be ignored as the options provided are not relevant to the
model, and the user cannot alter these settings.
Input Controls
The input controls allow the user to execute the Seattle Water Supply Model with a variety of
scenarios. Both operating rules and physical constraints can be adjusted to suit user needs. In
most cases, the default settings are those that were used to determine the system’s firm yield for
the base case (current) conditions. Four dashboards (Figures 16 – 19) are devoted to input
settings, and each can be accessed from any interface page via the buttons located on the left side
of the primary toolbar at the bottom of each page. For a complete list of the default values for
each input control, see Appendix F.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
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Seattle Supply System
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Figure 17. Cedar Reservoir Input Controls
Cedar Reservoir Controls
Cedar Rule Curve Option – This control sets the Cedar Reservoir rule curve's
maximum elevation. Four different options: 1560 ft (84,565 AF), 1562 ft
(88,460 AF), 1563 ft (90,449 AF), and 1590 ft (154,800 AF).
Pump Option – If activated, this control allows pump activation when the elevation of
Chester Morse Lake falls to 1534 ft. This effectively lowers dead storage
elevation from 1532 ft to 1517 ft.
Cedar Switching Option – The user can select the method of calculating critical
instream flow rates by comparing current flow rates to either 8-week or 13-week
instream flow averages.
Bypass Reach Minimum Flow – These flows (cfs) represent releases required from
Chester Morse to meet instream flow (fish) requirements through the bypass
reach.
Surcharge Option – This switch allows the Cedar to surcharge. The "Emergency
Spillway Trigger" defines amount of surcharge.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Minimum Percentage of M&I Demand Supplied by Cedar Reservoir – This is the
minimum percentage of “final demands” (M&I demands, firm supply, and
highline recharge requirements) supplied by the Cedar Reservoir. The control is
typically set at 30% due to the physical constraints of the system.
Emergency Spillway Volume Trigger – The emergency spillway gates are triggered at
this volume.
Figure 18. Tolt Reservoir Input Controls
Tolt Reservoir Controls
Tolt Reservoir Minimum Drawdown Elevation (Dead Storage) – This control offers
three different dead storage elevations for the Tolt Reservoir: 1710 ft (15,745
AF), 1690 ft (8,228 AF), and 1660 ft (1,519 AF). The latter two alternatives are
being investigated as feasible, future options that would provide additional
supply, but make treatment more difficult due to increased turbidity levels.
Tolt System Fixed Fish Option – Users can determine the conditions in which the South
Fork Tolt River will switch to critical instream flow requirements. Options
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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include switching by rules, switching during specified time periods, or no
switching.
Tolt System Reliance on Cedar – As an alternative, this control allows the critical
instream flow switch to rely on conditions in the Cedar System, instead of those
in the Tolt System.
Tolt Pipeline Option – This control specifies the capacity of the Tolt delivery system.
By default, the value is 120 mgd, the capacity of Tolt Pipeline 2.
Minimum Percentage of M&I Demand Supplied by Tolt Reservoir – This is the
minimum percentage of “final demands” (M&I demands, firm supply, and
highline recharge requirements) supplied by the Tolt Reservoir. The control is
typically set to 25% due to the physical constraints of the system.
Figure 19. Supplemental Supply Input Controls
Supplemental Supplies
Seattle Well Option – This option allows for use of the Seattle’s wells as a supply
source.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Seattle Maximum Well Pumping Capacity – This is the rate (mgd) at which the Seattle
Wells deliver water.
Recharge Option – This switch determines if Seattle Wells will be artificially recharged
with water from the Cedar River system.
Recharge Capacity – If the Seattle wells are to be recharged, this sets the rate (mgd) at
which the Seattle Wells will be artificially recharged.
Lake Youngs Option – In addition to regulating storage, the user can choose to use Lake
Youngs as a supply source. This is the Lake Youngs Drawdown alternative and
can potentially provide an additional 17,390 AF of supply storage.
Reuse Option – By implementing this alternative, water would be withdrawn from Lake
Washington and recycled for potable use.
Other Deliveries – The system can benefit from additional deliveries from unspecified
sources by activating this control.
Firm Supply Schedule – Firm supply is the flow requirement that exists in addition to
M&I and instream flow demands. Schedule options include year round, during
water weeks 1 – 35, or during water weeks 10 – 26.
Firm Supply Capacity – The user can limit the amount (AF/wk) of firm supply required.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Figure 20. Demand Input Controls
Demand Controls
Base M&I Demand – This is the annual average municipal and industrial demand. The
default value is 171 mgd, the firm yield of the current system. Actual demand
varies by month as a portion of this annual average.
M&I Curtailments – The user can impose voluntary or mandatory curtailments on the
system. M&I demand decreases by a percentage, specified for each month, of the
non-restricted demand.
Maximum M&I Augment – There is a maximum average annual surplus flow past
Landsburg that can augment releases from the Cedar Reservoir. This average
annual value is multiplied by the monthly demand factor to obtain the maximum
surplus value for each month.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Run Controller
The run controller (Figure 21) starts a run and displays the progress of a simulation. In addition
it can also be used for navigation, however, the buttons located along the bottom of each
dashboard screen are more convenient for navigating between dashboards.
Figure 21. Run Controller
The model itself can be viewed by selecting the “Go” button, located on the Run
Controller, and selecting “Go to Model Root.” This will activate upper-most level of the model
(Figure 22). At this level, open boxes (a box is also called a “container” in GoldSim), can be
explored in more detail by clicking on the “+” sign at the upper left-hand corner of the icon.
There are brief descriptions in several of the model containers written in text boxes. To return to
the user interface, click the “Go” button on the run controller, and then select
“Main_Page_Introduction” (or any of the dashboards, listed under the Model Root).
Figure 22. Upper-Most Level of the Seattle Water Supply System Model
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
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Seattle Supply System
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To run the model, adjust all input values as desired, and then select the “Run” button on
the Run Controller, which is the second button from the left, along the bottom. The simulation
runs regardless of what part of the model is being viewed. As the model is executing, progress in
illustrated on the red bars on the Run Controller. The date being simulated is also displayed on
the Run Controller (below the red bars), and the elapsed time is shown to the right of the red
bars. When the run is completed, a small window will appear on the screen with the message,
“Simulation Complete!”
System Outputs
Buttons to the right of the Run Controller are used to view the results of a simulation. There are
three main dashboards for viewing simulation outputs: Reservoir Storages, Minimum Instream
Flows, and Municipal and Industrial Flows. Each button directs the user to a screen which
contains more information on the specified part of the Seattle Supply system. Each output
dashboard contains numerical displays of results, as well as buttons that present charts or tables
of results when selected. Areas of interest in graphical displays can be magnified by holding
down the keyboard control (Ctrl) button while selecting the desired area with the left mouse
button. In the upper left corner of the chart/table windows, there are options to export, copy,
print, view properties, change font size, etc.
Reservoir Storages
The “Reservoir Storages” dashboard
provides a graphical overview of the
performance of the Cedar and Tolt
Reservoirs, as well as Lake Youngs when
it is in use. As previously noted , the
upper left hand corner of chart windows
provides many useful options, including
the “Table View” option that displays a
table of numerical values from which these
Figure 23. Cedar Reservoir Storages
graphs are composed. The six storage display
buttons are as follows:
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Cedar Storages – This graph displays volume of water stored (AF), rule curve (AF),
dead storage level (AF), and active capacity (AF) values for the Cedar Reservoir
(Chester Morse Lake and the Masonry Pool) as they change throughout the
simulation duration (Figure 23).
Tolt Storages – This graph displays volume of water stored (AF), rule curve (AF), dead
storage level (AF), and active capacity (AF) values for the South Fork Tolt
Reservoir as they change throughout the simulation duration.
Combined Reservoir – This graph displays the total volume of water (AF) in reservoir
storage (combined Cedar and Tolt Reservoir storage) as it changes throughout the
simulation duration.
Lake Youngs – This graph displays the total volume of water (AF) in stored in Lake
Youngs as it changes throughout the simulation duration.
Cedar Deliveries – This graph displays of the amount of water (AF/week) in the Cedar
Reservoir that is available for municipal and industrial needs, as well as the
minimum delivery (AF/week) the Cedar Reservoir must supply at a given time
(30% of M&I demand).
Tolt Deliveries – This graph displays of the amount of water (AF/week) in the South
Fork Tolt Reservoir that is available for municipal and industrial needs, as well as
the minimum delivery (AF/week) the Tolt Reservoir must supply at a given time
(25% of M&I demand).
Minimum Instream Flows
The Minimum Instream Flows
dashboard (Figure 24) provides
several useful statistics regarding the
ability of the system to continuously
meet instream flow requirements in
the Cedar and South Fork Tolt
Rivers. A shortfall is an event in
which the system is unable to meet
these requirements. The following
Figure 24. Minimum Instream Flow Output Statistics
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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six statistics regarding shortfalls are displayed for each river:
Total Number – The total number of shortfall events on each river is reported. An
“event” may last an indefinite period of time.
Cumulative Volume – The cumulative volume (AF) of shortfalls for each river is the
amount of water that the system was unable to supply over the span of all shortfall
events throughout the simulation duration.
Average Volume – The average volume (AF) of shortfall is the cumulative volume of
shortfalls divided by the total number of shortfall events.
Total Duration – The total duration (days) of shortfalls is the cumulative amount of real
time in which the system is unable to meet instream flow requirements.
Maximum Event Volume – The maximum event volume (AF) is the amount of water
not supplied in the single, greatest shortfall event. This does not necessarily
correspond to the event of longest duration.
Maximum Event Duration – The maximum event duration (days) is the total amount of
time, from start to finish, that the single, greatest shortfall event lasts. This does
not necessarily correspond to the event of greatest volume.
Graphs – The minimum instream flow graphs display the volume and timing of shortfall
events for each river.
Municipal and Industrial Demand
Statistics are also provided on system
performance as it pertains to municipal and
industrial flows (Figure 25). Again, a
shortfall is denoted each time the system is
unable to meet municipal and industrial
demands. The same six statistics regarding
shortfalls and one graph are displayed for
Figure 25. Municipal and Industrial Demand Output
Statistics
the Seattle Supply System’s ability to meet
M&I demands.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Additional Resources
GoldSim provides useful references for more detail on modeling in the GoldSim environment.
These manuals can be viewed by contacting GoldSim or the Water Resources Management and
Drought Planning Group (see below). GoldSim also provides an excerpt from their User Manual
online and other useful resources (e.g. QuickTour), which can be found on their website
(http://www.goldsim.com/).
Contact
Lee Traynham
Water Resources Management and Drought Planning Group (http://www.tag.washington.edu)
Department of Civil and Environmental Engineering
University of Washington
Box 352700
Seattle, Washington 98105-2700
TraynL@u.washington.edu
206.616.1775
Or
Dr. Richard Palmer
Water Resources Management and Drought Planning Group (http://www.tag.washington.edu)
Department of Civil and Environmental Engineering
University of Washington
Box 352700
Seattle, Washington 98105-2700
palmer@u.washington.edu
206 685-2658
Sources
"2007 Water System Plan." 20 JUL 2006. Seattle Public Utilities. 2 AUG 2006.
<http://www.seattle.gov/util/stellent/groups/public/@spu/@usm/documents/webcontent/s
pu01_002156.pdf>
“Demographics and Water Use Statistics.” Seattle Public Utilities. AUG 2006.
<http://www.seattle.gov/util/About_SPU/Water_System/History_&_Overview/DEMOG
RAPHI_200312020908145.asp>.
“Firm Yield of Seattle’s Existing and Alternative Water Supply Sources.” Seattle Public
Utilities. April 2006.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
33
Stein, Allan J. “Seattle voters authorize Cedar River Water Supply system on July 8, 1889.” 1
JAN 2000. HistoryLink.org. AUG 2006.
<http://www.historylink.org/essays/output.cfm?file_id=2123>.
“Water System History.” Seattle Public Utilities. 2 AUG 2006.
<http://www.seattle.gov/util/About_SPU/Water_System/History_&_Overview/WATERS
YST_200312020908156.asp>.
Figure Sources
Figure 1
“Seattle voters authorize Cedar River Water Supply system on July 8, 1889.” 1 JAN 2006.
HistoryLink.org. AUG 2006. <www.historylink.org/db_images/aln060.jpg>.
Figure 2
Kimbrough, R.S., Ruppert, G.P., Wiggins, W.D., and Smith, R.R. “Water Resources
Data-Washington Water Year 2004: U.S. Geological Survey Water Data Report
WA-04-1.” USGS. SEP 2006. <http://pubs.usgs.gov/wdr/2004/wdr-wa-041/pdf/wa00103ADR_Fig20.pdf.>
Figure 3
“Cedar River Watershed Virtual Tour.” Seattle Public Utilities. SEP 2006.
<http://www2.cityofseattle.net/util/tours/CedarRiverTour/slide10.htm.>
Figure 4
“The Crystal Model: Seattle’s Water Supply System.” Water Resources Management and
Drought Planning Group, Department of Civil and Environmental Engineering,
University of Washington. SEP 2006.
<http://www.prism.washington.edu/crystal/SeattleSystem.html>.
Figure 6
“The Crystal Model: Seattle Moraine Seepage.” Water Resources Management and Drought
Planning Group, Department of Civil and Environmental Engineering, University of
Washington. SEP 2006.
<http://www.prism.washington.edu/crystal/SeattleMoraineSeepage.html>.
Figure 7
“Cedar River Watershed Virtual Tour.” Seattle Public Utilities. SEP 2006.
<http://www2.cityofseattle.net/util/tours/CedarRiverTour/slide14.htm>.
Figure 9
Kimbrough, R.S., Ruppert, G.P., Wiggins, W.D., and Smith, R.R. “Water Resources
Data-Washington Water Year 2004: U.S. Geological Survey Water Data Report
WA-04-1.” USGS. SEP 2006. <http://pubs.usgs.gov/wdr/2004/wdr-wa-041/pdf/wa00103ADR_Fig21.pdf>.
Figure 10
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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“Tolt River Watershed Virtual Tour.” Seattle Public Utilities. SEP 2006.
<http://www2.cityofseattle.net/util/tours/ToltVirtualTour/slide15.htm>.
Figure 12
“National Gold Award: Tolt Treatment Facility.” 17 JAN 2002. Seattle Daily Journal of
Commerce. AUG 2006. <http://www.djc.com/news/ae/11129595.html>.
Figure 14
Banton, David and Chris Pitre. “Water Storage Goes Underground.” 25 JULY 2002. Seattle
Daily Journal of Commerce. AUG 2006. http://www.djc.com/news/ae/11129595.html>.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Appendix A: Seattle Regional Water Supply System
Source: "2007 Water System Plan." 20 July 2006. Seattle Public Utilities. 2 AUG 2006.
<http://www.seattle.gov/util/stellent/groups/public/@spu/@usm/documents/webcontent/spu01_002156.pdf>
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Appendix B: Inflow Locations
Inflow
Label
Associated
USGS Gauge
Cedar 1
12115000
Cedar River near Cedar Falls
Cedar 18
12115700
12115800
12116100
Gaines between USGS 12115000 and Water balance
masonry pool
Cedar 2
12116500
12117500
Natural inflow between Masonry
Dam and Landsburg
Water balance
Local inflow into Lake Washington,
including loss to evaporation
Water balance
Cedar 4
Flow Description
Cedar 3
12117500
Natural inflow between Landsburg
spawning channel and Lake
Washington
Cedar 5
12119000
Natural inflow between Landsburg
spawning channel and Lake
Washington
Tolt 7
12147600
Headwater flows near Index
Tolt 20
Tolt 8
12148000
Volume Calculation
Method
Gauged data calculated using
12111150; From 1929 to
1945 water balance using
other gages used.
Local inflows into Tolt Reservoir
Determined from river basin
characteristics
All flows between reservoir and
Carnation
Determined from river basin
Source: “The Crystal Model: Seattle Hydrologic Data.” Water Resources Management and
Drought Planning Group, Department of Civil and Environmental Engineering, University of
Washington. <http://www.prism.washington.edu/crystal/SeattleHydroData.html>. AUG 2006.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
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Appendix C: Cedar Minimum Instream Flow Requirements and
Rule Curve
Source: “Firm Yield of Seattle’s Existing and Alternative Water Supply Sources.” Seattle
Public Utilities. April 2006.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Seattle Supply System
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Appendix D: Tolt Minimum Instream Flow Requirements and Rule
Curve
Source: “Firm Yield of Seattle’s Existing and Alternative Water Supply Sources.” Seattle
Public Utilities. April 2006.
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington
Appendix E. Sample GoldSim Dashboard
Input Dashboard
Navigation Buttons
“Run” button
“Go” button, navigates
between the User
Interface and model
Output Dashboard
Navigation Buttons
Appendix F: Seattle Water Supply Model Default Input Values
Cedar Reservoir Controls
Cedar Rule Curve Option
Pump Option
Cedar Switching Option
Bypass Reach Minimum Flow
Surcharge Option
Minimum Percentage of M&I Demand Supplied
Emergency Spillway Volume Trigger
1560 ft (84,565 AF)
Switch Off
13-week
0 cfs
Switch Off
30%
1560 ft (84,565 AF)
Tolt Reservoir Controls
Tolt Reservoir Minimum Drawdown Elevation
1710 ft (15,745 AF)
Tolt System Fixed Fish Option
Option 2 - No Switching
Tolt System Reliance on Cedar
Switch On
Tolt Pipeline Option
Minimum Percentage of M&I Demand Supplied
120 mgd
25%
Supplemental Supplies
Seattle Well Option
Seattle Maximum Well Pumping Capacity
Recharge Option
Recharge Capacity
Switch On
10 mgd
Switch On
5 mgd
Lake Youngs Option
Switch Off
Reuse Option
Switch Off
Other Deliveries
Switch Off
Firm Supply Schedule
Option 0 – Year round
Firm Supply Capacity
0 AF/wk
Demand Controls
Base M&I Demand
171 mgd
M&I Curtailments
Option 0 – No Curtailments
Maximum M&I Augment
90 mgd
Seattle Supply System
41
Water Resources Management and Drought Planning Group - Department of Civil and Environmental Engineering
University of Washington