Incorporating Thermal Heterogeneity into Climate Vulnerability Assessments for Coastal Pacific Rivers

Aimee Fullerton, Se-Yeun Lee,C. Torgersen, and J. Lawler

Thermal regimes vary dramatically over time and those temporal signals vary over space

Steel et al. 2017

• Land use activities

• Climate change

Humans have altered riverine thermal landscapes

°C

1940 to 2010

July water temperature

Tem

pera

ture

J F M A M J J A S O N D

Salmon are affected by water temperature in each life stage

At broad spatial scales, water temperature influences species distributions

D. Isaak, US Forest Service

At fine spatial scales, water temperature influences growth, survival and connectivity among essential habitats

R. Faux, Quantum Spatial

Consequences of thermal stress

• Adults:• Decreased fitness• Straying or delay• Prespawn mortality

• Juveniles/smolts:• Altered growth rates• Altered ecological interactions

• Both:• Susceptibility to disease• Shifts in phenology

Keefer et al. 2015

Salmon can seek cooler water

Adult steelhead use cold tributaries during upstream migration

Juveniles also thermoregulate

Photo: J. Ebersole, USEPA

Managing for coldwater habitats

• Primer for locating existing and potential cold water refuges

• Need to consider how coldwater habitat may change in the future

• Ultimate goal is to understand and manage “sufficient” coldwater habitat for salmonids

Objectives

1. Characterize thermal heterogeneity (“patchiness”) in rivers

2. Assess potential future thermal heterogeneity

3. Illustrate salmon vulnerability to loss of cold patches

Larger rivers, summer

afternoons

Snoqualmie

Siletz

Airborne thermal infrared (TIR)

surveys of rivers

Thermal patterns at different

spatial scales

SpacingLength

Δ Temp.

Distance upstream (km)

Reach

Localized inputs

Channel unit

Profile shape

Distance upstream (km)

Wa

ter t

emp

era

ture

(C)

Segment

Networkrange

diversity

migration

refuge

Distance upstream (km)

Wa

ter t

emp

era

ture

(ºC

)

>20 °C15-20 °C<15 °C

cool patches

too hot

Within-river thermal heterogeneity

downstream upstream

• Lots of warm habitat, but also a huge amount of thermal diversity among and within rivers

• Many small cool patches distributed throughout warmer habitat, mostly in upstream reaches

• Cool patches generally large enough and within swimming distance for salmon in many (but not all!) rivers

>20 °C 15-20 °C <15 °C

Resolution (km)

raw data

3-km

1-km

Patch density

Patch length

Patch spacing

What if we don’t have spatially continuous data?

There may also be relative refuges

Distance upstream (km)

Wat

er te

mpe

ratu

re (º

C)

10-km moving average

Warmer than average

Cooler than average

cooling reach (100-m)

warming reach

Localized cooling/warming trends

s1s2

s3

c1

Tail-up

Spatial Stream Network Model

Ver Hoef and Peterson 2010

Wat

er te

mpe

ratu

re (º

C)

WA OR CA

Distance upstream (km)

Observed (remotely sensed)

Predicted (NorWeST)

Example long profile comparisons

Snoqualmie

Siletz

10 km

10 km

Snoqualmie

Siletz

Remotely-sensed(TIR)

NorWeST

10 km

10 km

cool patches (<15 ºC)

downstream-most patch

Objectives

1. Characterize thermal heterogeneity in rivers

2. Assess potential future thermal heterogeneity

3. Illustrate salmon vulnerability to loss of cold patches

How might climate change alter results?

salmonguy.org

3 Methods

1. Simple Shift

2. Random forest models (statistical)

3. DHSVM-RBM (process-based model)

Method 1: Simple Shift.Warm year patterns resemble cool year patterns

<15 ºC

15-20 ºC

>20 ºC

TIR + 2 ºC Change

becomes >15 ºC

becomes >20 ºC

Simple shift

Remotely-sensed (TIR)

Simple Shift

• More warm habitat, less cool habitat

• Some warm patches will get much larger as small intervening cool patches disappear

• Correspondingly, the distance between cool patches will increase for some rivers

Simple Shift

Wat

er te

mpe

ratu

re (º

C)

Distance upstream (km)

TIR + 2 ºC

Snoqualmie

Siletz

>20 °C, stressful15-20 °C, tolerable<15 °C, optimal

Remotely-sensed (TIR)

Simple Shift

10 km

10 km

Snoqualmie

Siletz

TIR + 2 ºCcool patches (<15 ºC)

downstream-most patchRemotely-sensed

(TIR)

Δ Air temperature 2080s, rcp 8.5

Δ Probability of precipitation as snow 2060s, rcp 8.5

Δ Precipitation2080s, rcp 8.5

Method 2: Statistical modelingWe know climate varies spatially, so

incorporate expected climate predictions

Random forest

1. Fit trend: WT~ climate variables

residuals

trend

3. Sum:

resid-uals

future trend

future heterogeneity

2. Predict future trend

Δ max air tempΔ mn ann pptΔ snow prob

Random forest

Historical 2080s

Random forest

• Fewer patches 15-20 °C

• More variance in warm patch size (some become very large)

• Similar spacing(overall)

>20 °C 15-20 °C <15 °C

downstream upstream

19992080s

20012080s

Random forest

Less cool habitat in the 2080sLocations of cool patches shift

Tualatin River; 121 km

Chiwawa River; 53 km

(Source: Sun et al. 2015)

Water Temperature Model (RBM)

Hydrology Model(DHSVM)

Explicit representation of topography & vegetation Physically consistent picture of flow & temperature Resolution: 150 m and 3 hour time step

Method 3:Process-based model, DHSVM-RBM

DHSVM-RBM

Calibration for the Siletz River

Historical SimulationObservation DHSVM-RBM

Calibration for the Snoqualmie River

Historical SimulationObservation DHSVM-RBM

Changes in Spatial Water Temp Patternfor the Siletz River

Future Patterns(2080s, RCP 8.5)

Historical Patterns

DHSVM-RBM

Changes in Spatial Water Temp Patternfor the Siletz River

Future Patterns(the 2080s RCP 8.5)

Historical Patterns

DHSVM-RBM

Historical Patterns

Changes in Spatial Water Temp Patternfor the Snoqualmie River

DHSVM-RBM

Future Patterns(the 2080s, RCP 8.5)

Historical Simulation (1990s)2080s, RCP 8.5

Siletz River, OR Snoqualmie, WA

Changes in Streamflow

DHSVM-RBM

Changes in coldwater patches

Siletz Snoqualmie

>20 °C, stressful15-20 °C, tolerable<15 °C, optimal

Historical

2080s, RCP 8.5

DHSVM-RBM

Wat

er te

mpe

ratu

re (º

C)

Distance upstream (km)

Sim

ple

Shift

Rand

om F

ores

tDH

SVM

-RBM

Siletz Snoqualmie

Historical Simulation2080s, RCP 8.5

Changes in water temperaturepredicted by 3 different approaches

Objectives

1. Characterize thermal heterogeneity in rivers

2. Assess potential future thermal heterogeneity

3. Illustrate salmon vulnerability to loss of cold patches

• Many salmonids• TMDLs in development

Maximum water temperatureAugust 2001

Siletz River

Application: Cold-water Habitat Vulnerability Assessment

Cold water patches, 2001 Cold water patches, 2080s

10 kmcool patches (<15 ºC)

downstream-most patch

summer steelheadJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Upstream migrationAdults hold

SpawnEggs incubate & fry emerge

Juveniles rearSmolts outmigrate

Assess spatial and temporal distribution of life stages by species

spawning & rearingrearing & migration

Vulnerability (cold patch assessment)Species Current Future

Fall Chinook-adults 2.0 2.5-juveniles 2.2 2.7

Spring Chinook-adults 1.9 2.3-juveniles 1.7 2.1

Summer Steelhead-adults 4.2 4.2-juveniles 1.8 1.8

Winter Steelhead-adults 0 0-juveniles 1.8 2.3

Coho-adults 3.7 4.7-juveniles 1.9 2.3

Chum-adults 0 0-juveniles 0 0

V = SES = sensitivity (level of impairment at

water temperature)E = exposure; see below(and adaptability; not included)

p = life stage presence during Augustu = use of habitat during Augustn = cold patch abundance scores = cold patch spacing score

E = p(u + n + s)

Takeaways• Stream temperature is diverse across

space and over time

• Spatiotemporal patterns in water temperature have biological and ecological consequences

• Many recent advances in data and tools predict how climate change may alter thermal landscapes and affect biota

Management Applications

• Water temperature regulations (i.e., the TMDL planning process)

• 5-year status reviews and recovery plans for ESA-listed salmon and steelhead

• Prioritizing riparian and habitat restoration

• Climate-ready adaptation planning

1. PLAN• Characterize historical distribution of suitable

habitats (a baseline for targeting restoration)• Evaluate the sufficiency of habitats for supporting

salmon migration and rearing• Identify impaired locations and time windows• Consider expectations given climate change

2. ACT• Prioritize actions according to threat/risk level• Implement conservation activities• Monitor and evaluate effectiveness and

biological response

What can we do to conserve thermal diversity in streams?

Thanks to:

and to:

Emily AlfredJoe Ebersole

Russ FauxDan Miller

Ashley Steel

Additional Resources• EPA Columbia River Cold Water Refuges Project

https://www.epa.gov/columbiariver/columbia-river-cold-water-refuges

• NW Power Planning Council Presentation https://www.nwcouncil.org/news/blog/cold-water-habitat-april-2017/

• EPA Primer for Identifying Cold Water Refuges https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=243611

Fullerton, A.H., C.E. Torgersen, J.J. Lawler, J.L. Ebersole, and S.Y. Lee. In Press. Longitudinal thermal heterogeneity in rivers and refugia for coldwater species: Effects of scale and climate change. Aquatic Sciences.

Fullerton, A.H. C.E. Torgersen, J.J. Lawler, R.N. Faux, E.A. Steel, T.J. Beechie, J.L. Ebersole, and S.G. Leibowitz. 2015. Rethinking the longitudinal stream temperature paradigm: region-wide comparison of thermal infrared imagery reveals unexpected complexity of river temperatures. Hydrological Processes 29:4719-4737.

Steel, E.A., T.J. Beechie, C.E. Torgersen, and A.H. Fullerton. 2017. Envisioning, quantifying, and managing thermal regimes on river networks. BioScience 67:506-522.

Isaak, D.J. et al. 2017. The NorWeST summer stream temperature model and scenarios for the western US: a crowd-sourced database and new geospatial tools foster a user community and predict broad climate warming of rivers and streams. Water Resources Research. DOI 10.1002/201WR020969.

Sun, N., J. Yearsley, N. Voisin, and D. P. Lettenmaier. 2015. A spatially distributed model for the assessment of land use impacts on stream temperature in small urban watersheds. Hydrological Processes 29:2331-2345.

53

10 km

steelheadJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Upstream migration (summer)migration (winter)

SpawnEggs incubate & fry emerge

Juveniles rearSmolts outmigrate

Estuary

Cold water patches, 2006 Cold water patches, 2080s

Species Current FutureChinook

-adults 2.7 2.8-juveniles 2.5 2.5

Steelhead-adults 5.5 5.5-juveniles 3.0 3.0

Coho-adults 4.9 4.5-juveniles 2.5 2.5

Pink-adults 5.5 5.5-juveniles 0 0

Chum-adults 0 0-juveniles 0 0