California's Delta and the Future of Statescale Water Supplies

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California's Delta and the Future of State-scale
Water Supplies
Mike Dettinger USGS/SIO
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California's Water Supplies

• 75 of runoff occurs in north
• 72 of consumptive use in south

Sacramento-San Joaquin Delta Watershed
http//www.water.ca.gov/maps/allprojects.html
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Uses of the Major Water Projects
Agriculture Urban
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Water Sources for Urban Southern California
New CR Xfers
Delta
Metropolitan Water District Urban Water
Management Plan, 2005
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NORTH
San Joaquin R
Delta
Sacramento R
Bay
In today's State-scale water-supply system, the
Delta is the critical, but weak, link between
North South
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• The Delta is a 2200 km2 maze of
• Farms
• Channel sloughs
• Marshlands
• Suburban
• Encroachment

all sitting very near sea level with water held
in place by aging, poorly engineered levees
50 km
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High quality Sacramento River
Delta as the North-South Meeting Place of Waters
?
Salty seawater
Low quality San Joaquin River
Water pumped south
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• The Big Gulp
• In the event of several major levee breaches,
  sea water is expected to flow in and cutoff
  passage for southbound freshwater flows to the
  export pumps in the southern Delta ()
• Sea-level rise, increased flood flows, aging
  levees, earthquakes together offer an estimated
  60 chance of this happening by 2050 (Mount
  Twiss, 2005)

The Big Gulp
Florsheim Dettinger, 2005
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ECOSYSTEMS Endangered fisheries, shrinking
wetlands declining landscapes have devastated
the once-rich ecosystems of Central California.
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Outflows and Diversions from the Delta
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Outflows and Diversions from the Delta
Slightly over 20 MAF
Slightly over 20 MAF
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Sources and Fates of Dissolved Organic Carbon in
the Delta
Luoma et al., 2008
DOM in treated water ends up contaminating with
byproducts like THMs (NOT GOOD!)
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DRIVERS of DELTA CHANGE

• Land subsidence
• Invasive species
• Population growth urbanization
• Earthquakes
• Climate change
• Sea level rise

Pelagic organism declines (POD) Less reliable
water supplies Deteriorating water
quality Threats to agriculture, communities
infrastructure corridors
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What should the future Delta look like?
Mount, Twiss Adams, 2006
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• Business as Usual?
• Ecosystem's piece of the Pie?
• Crumbling Levees "The Big Gulp"

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• Fortress Delta?
• Astronomical cost!
• Sea-Level Rise Receding Targets
• Ecosystems are adapted to variable flows
  salinity (not Delta as concrete canal)

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• Abandoned Delta?
• Peripheral Canal !
• (Voters rejected in 1982, but its back!)
• Ecosystem or sewer?
• 560,000 acres of prime agriculture 2B
  (in-Delta) agricultural economy

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• Restored Delta?
• Restored to what?
• Sea level rise, invasive species sediment
  supply
• Would this provide water supply reliability?
  Infrastructure corridors?

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Governors Blue Ribbon Delta Visions
Panel conclusions (2008)

• 3. Dual conveyance Leaky peripheral canal
  variable salinity Delta
• 4. Re-governance the Delta
• 5. STOP suburbanization!
• 6. Armored levees where needed (human life),
  abandoned levees for ecosystems over-toppable
  levees for agriculture
• 7. Variable flow regimes geomorphology
• 8. Carbon "farms"?

• Coequal water supply ecosystem goals
• 2. Dual conveyance facilities (instead of BAU or
  isolated Delta, both!)