CASCaDE

A Tool for Examining the Effect of Climate Change on the San Francisco Delta Ecosystem

USGS:

Daniel Cayan, Jim Cloern, Mike Dettinger, Neil Ganju, Bruce Jafee, Noah Knowles, Lisa Lucas, Sam Luoma, Nancy Monsen, Francis Parchaso, Dave Peterson, Dave Schoellhamer, Robin Stewart, Jan Thompson

Collaborators:

Bill Bennett, Mark Stacey, Mick van der Wegen,Wayne Wagner, Christa Woodley

Our question: How do we inform management and restoration decisions about changing climate in a system where water supply and ecosystem function must be balanced?

• Largest Pacific estuary• 150,000 km2 watershed• Drinking water for 23 million• $30B agricultural industry• 8th

largest economy ??• At risk from levee failures• Largest tidal wetland in west•

Habitat for endangered species•

Site of 2 large scale restoration programs

Decisions are particularly difficult when so many anthropogenic and natural changes are occurring at a rapid rate. For example, we need to plan for challenges to our restorationsites,

…the planned and current water conveyance structures,

…and for catastrophic changes due to earthquakes and storms.

CASCaDE

ProjectComputationalAssessments ofScenarios

ofChange

in theDeltaEcosystem

We chose to build a series of tools to look at scenarios of change (NOT predictions) –

we

can change scenarios

Climate Change

Sea-Level Rise

Structural ChangesCASCaDE’s

strength is in

the interrelated 'cascade' of models

• Integrate processes

•

Characterize responses to simultaneous forcings

•

Highlight critical sensitivities

In response to our scenarios, we look at trends, thresholds, and indices that are relevant to ecological processes or management.

We started by targeting four climate scenarios from amongst 100+ recent climate-change projections

Consistent with California Climate Scenarios Assessment, 2006 and 2008• Medium warmer and drier

(GFDL-B1)‏

• Much warmer and drier

(GFDL-A2)‏

• Not so much warmer with no ppt

change

(PCM-B1)‏

• Medium warmer with no ppt

change

(PCM-A2)‏

Cayan et al,2006

Mike Dettinger, Dan Cayan

We will look at three examples where we use scenarios of climate change to illustrate how these changes cascade through to ecological changes.

Major RiversState ProjectsFederal ProjectsLocal Projects

The California Water Atlas (1978)

Noah Knowles: Watershed Model withOperations

# 1 Water Supply

Snowpack trends for all scenarios is shown to diminish as more of the precipitation arrives as

rain.m

m S

WE

mm

SW

E

Noah KnowlesJan 29, 1PM, Session A

GFDL-A2 Reservoir Storage

The resulting downward trend in reservoir storage has implications to the Delta ecosystem.

North

South

GFDLA2 - Exports

y = -2.26x + 12052

2001 2011 2021 2031 2041 2051 2061 2071 2081 2091

CFS

0

.5

1

1.5

2

The reduction in reservoir storage will result in reduced freshwater into the Bay and an overall trend downward in exports.

http://www.chinadaily.com.cn/china/2006-08/17/xin_3308031717203692474511.jpg

The system is presently “maintained”

by dikes that may breach at single locations or catastrophically at multiple locations.

# 2 Structures

We find that under our scenarios, sea level rises considerably by 2100, which is likely to strain natural and anthropogenic structures.

GFDL A2+ 0.9 m

Dan Cayan: Global Climate and Sea Level Model Jan 29 8:50AM

The frequency of high open coast sea levels in combination with large fresh water flows will increase considerably. The resulting combination of increased sea level & storm surges may prove catastrophic to some structures and stressful to some wetlands & restorations.

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ocal

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The stress between water for people and water for the ecosystem will get greater.

# 3 Changing Salt Field

Have we altered the carrying capacity?

0

20

40

60

80

Abun

danc

e In

dex Delta Smelt

1960 1970 1980 1990 20000

20000

40000

60000

80000

100000Longfin smelt

The decline of some fish species has resulted in listing species as threatened/endangered, altering freshwater exports, and causing ecologists to question if this is a food, habitat or contaminants problem.

Feb-June GFDL A2

0

10

20

30

40

50

60

<64 >64<75 >75<81 >81X2 (km)

Freq

uenc

y

2001-20252026-20502051-20752076-2100

A salinity standard (X2) was developed to protect fish and water supply. The position of X2 in the estuary is correlated with the success of some fish species either due to habitat or food supply.

6475

81

Ouch!

Ouch!

A sample message: it will be more difficult to maintain the standard.

We can also look for thresholds and change in frequency of thresholds within a time series to develop trends in stress for fish and biota.

2000 2010 2020 2030 2040 2050 2060 2070 2080 2090

5

10

15

20

25

30

T max

[οC

]

gfdl b1

2000 2010 2020 2030 2040 2050 2060 2070 2080 20900

10

20

30

40

50

60

70

80

90

100

Day

s/Y

ear >

25ο C

Sac Hood

Larry BrownJan 30, 1:40PM, Session D

GFDLA2

y = -5E-06x + 0.172

0.01

0.10

1.00

20012006201120162021202620312036204120462051205620612066207120762081208620912096

SJR

/Sac

R

By looking at the trend in the ratio of the outflow of the two major rivers we can examine potential changes in contaminant sources to the Delta if the riverine

sources remain constant.

In this example we find the ratio to be constant.

That is interesting however…..

…ratios may mean little if present structures are altered or new ones built. Indices such as these give us a starting point for thought experiments while the hydrodynamic model can show us changes in mixing and transport.

N. Monsen

Nancy MonsenHydrodynamicModel

CASCADE was born from our desire to understand how climate change would interact with natural and anthropogenic changes in the system. It is not our goal to predict change. It was and is a tool building exercise. Second, by using scenarios we can examine trends and thresholds for systems most at risk without the ever present distraction of which climate model is best.

Where we started: “This is hard enough, let’s not make it harder.”