Reassembling Hetch Hetchy

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Re-assembling Hetch Hetchy?
Water Supply Implications of Removing
OShaughnessy Dam
Sarah Null Geography Graduate Group UC Davis
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Californias Hydrology and Water Challenges (in a
nutshell)

• Water Supplies
• 200 maf/yr precipitation
• 70 maf runoff
• Most runoff in the North
• Much water stored as mountain snowmelt
• Seasonal and Annual Variations in Quantity
• Conflict for Limited Resources
• Water Demands
• Agricultural uses
• Urban uses
• Environmental uses
• Most Urban and Ag demands in the South
• Water Quality
• Conflicts over water quality, not all water is
  alike

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California Water System
http//www.water.ca.gov/maps/allprojects.html
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Fallout

• Regional feuds over water allocation
• East vs. West North vs. South
• Agriculture vs. urban vs. environment
• Environmental problems
• California is dynamic problems and solutions are
  continually changing

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Primary Study Questions
Background
The Hetch Hetchy System provides water for San
Francisco and neighboring cities. OShaughnessy
Dam is one component of this system, providing
approximately 25 of water storage for the Hetch
Hetchy System and none of its conveyance.
Removing OShaughnessy Dam has gained interest to
restore Hetch Hetchy Valley and open it to
recreation and tourism.

• If OShaughnessy Dam were removed, could existing
  water facilities supply the Hetch Hetchy Systems
  service area with water?
• Would additional scarcity occur to other urban,
  agricultural, or environmental water users
  without OShaughnessy Dam?
• What hydropower revenues would be lost from
  removing OShaughnessy Dam?
• Would water quality costs increase from removing
  OShaughnessy Dam?

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History of the Hetch Hetchy System

• San Francisco earthquake (and ensuing fires)
  acted as a catalyst for the search for a stable
  water supply.
• Huge controversy when Hetch Hetchy Reservoir
  proposed (John Muir vs. San Francisco).
• Raker Act passed 1913 by Taft (allowed a dam to
  be built in a National Park).
• OShaughnessy Dam completed in 1923.

Michael OShaughnessys plans for San Franciscos
water system
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Hetch Hetchy Valley
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Reasons to restore Hetch Hetchy Valley
Hetch Hetchy Valley, 1908

• Hetch Hetchy Valley was nearly identical to
  Yosemite Valley prior to construction of
  OShaughnessy Dam.
• Water is scarce, but Yosemite Valley is also a
  scarce resource.
• Restoring Hetch Hetchy Valley could open an area
  equal to Yosemite Valley to wildlife and
  recreation.
• Recreation and tourism benefits may exceed water
  storage and hydropower benefits of the reservoir.
• Ethical and aesthetic reasons - should a
  reservoir for San Francisco be in Yosemite
  National Park?

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Study Region
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Yosemite National Park Map
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OShaughnessy Dam

• A Hetch Hetchy System component.
• About 25 of SFPUCs storage in the Hetch Hetchy
  System, 14 of storage on Tuolumne River.
• Operated primarily for water supply and
  hydropower production.
• Removal could open Hetch Hetchy Valley for
  restoration and recreation.
• Water is scarce, space in Yosemite Valley is also
  scarce.

• Water from OShaughnessy has filtration
  avoidance, meaning only minimal water treatment
  is necessary (chlorine or chloramine).

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Reservoir Capacities in the Hetch Hetchy System
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CALVIN economic-engineering model

• Minimizes economic costs within constraints
• Economic value functions for agricultural and
  urban uses
• Operating costs hydropower, water treatment,
  pumping, etc.
• Flow constraints for environmental uses
• Prescribes operation over a 72-year historic
  hydrology
• Surface and groundwater represented
• Major hydropower facilities
• Year 2020 projected demands and infrastructure
• Hypothetical inter-tie links New Don Pedro
  Hetch Hetchy Aqueduct

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Californias Water System
155 Major surface reservoirs Extensive
groundwater Vast conveyance network Vast
irrigated acreage 36 million people
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Policy Activities Included

• Surface reservoir operations
• Groundwater reservoir operations
• Water allocation (markets exchanges)
• Urban conservation/use efficiencies
• Cropping changes and fallowing
• Irrigation technologies efficiencies
• New technologies
• Wastewater reuse
• Seawater desalination
• Integrates wide range of options

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• Network Flow Optimization

Minimize (1) Z ?? cij Xij, Xij is flow
from node i to node j Subject to (2) ? Xji
? aij Xij bj for all nodes j (3) Xij ?
uij for all arcs (4) Xij ? lij for all
arcs cij economic costs (ag. or urban) bj
external inflows to node j aij gains/losses on
flows in arc uij upper bound on arc lij lower
bound on arc
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Data Flow for the CALVIN Model
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Model Limitations

• Ignores political and institutional constraints
• No flood control or recreational benefits, but
  current flood storage rules are respected
• Simplified costs, water quality, hydrology
• Operates reservoirs aggressively with perfect
  foresight

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Model runs
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Hetch Hetchy System Water Storagewith and
without OShaughnessy Dam
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Hetch Hetchy Aqueduct upstream of New Don Pedro
Seasonal Flow in Hetch Hetchy Aqueduct upstream
of New Don Pedro
Flow through New Don Pedro Inter-tie
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Hetch Hetchy System Schematic
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Water Scarcity

• No scarcity to urban areas.
• No scarcity to environmental demands.
• Small increase in scarcity to TID and MID (CVPM
  11 12) without OShaughnessy Dam.
• No scarcity to other agricultural demands.

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Average Deliveries, Scarcity, and Scarcity Cost
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Hetch Hetchy SystemHydropower Generation
Average annual difference 457 GWhr/yr Average
annual cost difference 11,107,050
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Water Treatment Changes

• Removing OShaughnessy Dam would prompt loss of
  regulatory filtration avoidance status, raising
  water treatment costs.
• Construction costs, about 1-2 billion (50-100
  million/year)
• OM costs, about 6 million/year.
• Filtration avoidance makes OShaughnessy very
  valuable.
• Water quality would remain high.

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Major Conclusions

• Removing OShaughnessy Dam need not substantially
  increase water scarcity.
• Capture of considerable runoff could be possible
  at the damsite for much of most years
• No effects outside the Tuolumne basin, if New Don
  Pedro Reservoir is connected directly with the
  Hetch Hetchy Aqueduct.
• Conveyance can sometimes substitute for water
  storage. (Intertie between New Don Pedro
  Reservoir and Hetch Hetchy Aqueduct)
• Loss of filtration avoidance would be very
  costly.
• Removing OShaughnessy Dam reduces hydropower
  generation and revenues.
• Optimization modeling helps identify promising
  re-operations for water resource systems
  potentially undergoing restoration.
• Politics and legal arrangements may be more
  limiting to the Hetch Hetchy System than physical
  constraints.

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More Conclusions(from a broader perspective)

• California will always have interesting evolving
  water problems
• Water supply engineering has changed with the
  evolution of Californias water supply problems
• The era of dam building is mostly over, future
  problems are more likely to be solved with
  creative management
• Coordinated use of existing water supplies
• Conjunctive use (of surface water and
  groundwater)
• Water transfers
• Water conservation technologies
• Water supply solutions will continue to change as
  problems continue to change
• Some challenges are regional

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Contact Information
Sarah Null senull_at_ucdavis.edu Doctoral
Student UC, Davis Geography Graduate Group
Thesis available online http//cee.engr.ucdavis.e
du/faculty/lund/students/SarahNullThesis.pdf Par
tially funded by the UC Davis John Muir Institute
for the Environment