San Pedro River, Arizona, National Geographic Magazine Projecting the Effects of Climate Projecting the Effects of Climate Change on Riparian Ecosystems in Change on Riparian Ecosystems in the Southwest: The Upper San Pedro the Southwest: The Upper San Pedro as a Case Study as a Case Study Mark Dixon Mark Dixon 1 1 and Juliet Stromberg and Juliet Stromberg 2 2 1 1 University of South Dakota University of South Dakota 2 2 Arizona State University Arizona State University Climate and Riparian Areas Workshop, Casa Grande, Arizona Climate and Riparian Areas Workshop, Casa Grande, Arizona April 11, 2007 April 11, 2007
47
Embed
Projecting the Effects of Climate Change on Riparian ...
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
San Pedro River, Arizona, National Geographic Magazine
Projecting the Effects of Climate Projecting the Effects of Climate Change on Riparian Ecosystems in Change on Riparian Ecosystems in
the Southwest: The Upper San Pedro the Southwest: The Upper San Pedro as a Case Studyas a Case Study
Mark DixonMark Dixon11 and Juliet Strombergand Juliet Stromberg22
11University of South DakotaUniversity of South Dakota22Arizona State UniversityArizona State University
Climate and Riparian Areas Workshop, Casa Grande, ArizonaClimate and Riparian Areas Workshop, Casa Grande, ArizonaApril 11, 2007April 11, 2007
San Pedro River, Arizona, National Geographic Magazine
River damming for water storage, hydropower, flood control
Surface water diversion
Ground water pumping from stream and regional aquifers
Over-use by cattle
Climate Change?
Human Impacts on SW Rivers
PrecipitationSnow
accumulationSnowmelt
Evapotranspiration
Infiltration & runoff
Mnt Front Recharge
Urban & AgWater demand
StreamDischarge
Projected Climate Change for SW by 2060 (SRAG 2000)
Hadley Center ModelCanadian Climate Centre ModelNCAR Regional Model
Season
0
1
2
3
4
5
6
Winter Spring Summer Fall
Season
Deg
rees
C
Change in Mean Temperature Change in Daily Precipitation
-1.5
-1
-0.5
0
0.5
1
1.5
2
Winter Spring Summer Fallm
m/d
ay-
1
-
0
1
2
3
4
5
6
Uncertainty in Future Climate
San Pedro River, Arizona, National Geographic Magazine
•• What are the potential effects of climate change What are the potential effects of climate change on riparian vegetation composition and on riparian vegetation composition and dynamics in the Southwest?dynamics in the Southwest?
•• Used the Upper San Pedro as a case studyUsed the Upper San Pedro as a case study
Research Question:Research Question:
THE UPPER SAN PEDRO (SE Arizona)
• One of few undammed, low elevation rivers in the SW US with perennial flow
• Biodiversity hotspot ( “Last Great Places”)• Valuable migratory bird habitat• Growing human population & riparian
ecosystem both depend on groundwater• Threats from groundwater overdrafts
San Pedro River, Arizona, National Geographic Magazine
What are the potential effects of climate What are the potential effects of climate change on riparian vegetation composition change on riparian vegetation composition and dynamics on the Upper San Pedro?and dynamics on the Upper San Pedro?
Research Question:Research Question:
Watershed Runoff Model (SWAT)
Channel Migration Model (MEANDER)
Stream Flow Projections
Daily Climate Land Cover
Site Conditions (Groundwater, etc.)
Projected Channel Migration
Riparian Vegetation Model
Projected Vegetation Change
Climate Change Scenarios
Watershed Runoff Model (SWAT)
Channel Migration Model (MEANDER)
Stream Flow Projections
Daily Climate Land Cover
Site Conditions (Groundwater, etc.)
Projected Channel Migration
Riparian Vegetation Model
Projected Vegetation Change
Climate Change Scenarios
Modeling Climate Change Effects• Simulate range of
transient climate change scenarios (2003-2102)
• Model effects of climate on physical processes (stream flow, channel migration)
• Model response of vegetation to changes in physical (and biotic) drivers
Climate Change Scenarios (2003-2102)
• No change over 1951-2002 conditions• Warm: Warmer (+5 º C), but no change in precipitation• Warm Wet: Warmer, 50% increase in winter precipitation • Warm Very Wet: Warmer, 100% increase in winter precip• Warm Dry: Warmer, 50% decrease in winter precipitation
• Transient scenarios, developed by modifying 1951-2002 daily weather time series
• Modeling sites that span the range of hydro conditions along Upper San Pedro
Kolbe (Perennial)
-3.0-2.0-1.00.01.02.03.04.05.06.0
0 10 20 30 40 50 60 70 80 90 100 110
Distance W to E (m)
Elev
atio
n ab
ove
Thal
weg
(m)
Plot Elev GW Deep GW ShallowPalominas UA (Wet Intermittent)
-3.0-2.0-1.00.01.02.03.04.05.06.0
-25 0 25 50 75 100 125 150 175 200 225 250
Distance W to E (m)El
evat
ion
abov
e Th
alw
eg (m
)Plot Elev GW Deep GW ShallowContention (Dry Intermittent)
-3.0-2.0-1.00.01.02.03.04.05.06.0
0 40 80 120 160 200 240 280 320 360 400 440
Distance W to E (m)
Elev
atio
n ab
ove
Thal
weg
(m)
Plot Elev GW Max Depth GW Min Depth
Kolbe (Perennial)
-3.0-2.0-1.00.01.02.03.04.05.06.0
0 10 20 30 40 50 60 70 80 90 100 110
Distance W to E (m)
Elev
atio
n ab
ove
Thal
weg
(m)
Plot Elev GW Deep GW ShallowPalominas UA (Wet Intermittent)
-3.0-2.0-1.00.01.02.03.04.05.06.0
-25 0 25 50 75 100 125 150 175 200 225 250
Distance W to E (m)El
evat
ion
abov
e Th
alw
eg (m
)Plot Elev GW Deep GW ShallowContention (Dry Intermittent)
-3.0-2.0-1.00.01.02.03.04.05.06.0
0 40 80 120 160 200 240 280 320 360 400 440
Distance W to E (m)
Elev
atio
n ab
ove
Thal
weg
(m)
Plot Elev GW Max Depth GW Min Depth
Modeling Watershed Runoff and Streamflow
• Flow scenarios– Ran calibrated basin runoff
model (SWAT) for the upper San Pedro basin for the five climate scenarios
• Jingle Wu and Alex Buyantuyev (Landscape ecology lab, ASU)
• Eric Larsen and Alex Fremier (UC-Davis) – Channel migration modeling
• Mariano Hernandez & Dave Goodrich (ARS) – help with SWAT model
• Jeff Price (CSU-Chico) and Hector Galbraith – Climate change project
• Funding by SAHRA, Department of Defense Legacy Program, Upper San Pedro Partnership, US EPA & American Bird Conservancy
Acknowledgments
1955
2002
1973
1978 1996
1983
• Traced channel centerline on historic aerial photos
• Calculated area “reworked” by the river between dates
• Related to historic flows (cumulative stream power) between photo dates
Quantifying Historic Channel Migration
Functions of FloodsFunctions of FloodsWinter floods (longer duration)Winter floods (longer duration)•• Move channelsMove channels•• Stimulate cottonwoodStimulate cottonwood--willow and sycamore recruitmentwillow and sycamore recruitment•• ReRe--soak floodplains and help sustain soak floodplains and help sustain baseflowsbaseflows
Summer floods (short duration)Summer floods (short duration)•• Stimulate growth of annual and perennial plants and Stimulate growth of annual and perennial plants and
recruitment of mesquiterecruitment of mesquite•• ReRe--soak floodplain and sustain soak floodplain and sustain baseflowsbaseflows•• Move leaf litter and stimulate decompositionMove leaf litter and stimulate decomposition
Possible Effects of Climate Change on Riparian Ecosystems
Increased temperatures• Longer growing seasons
• Expansion of mesquite and saltcedar to higher elevations?
• Higher evaporative demand and groundwater uptake by phreatophytes
• Higher water use by human ecosystems?
• Greater risk of groundwater decline, channel drying, and degradation of riparian zones?
Possible Effects of Climate Change on Riparian Ecosystems
Increased winter precipitation• Increased establishment of pioneer trees
(cottonwood, willow, salt cedar)
• Increased rates of river channel migration
• Increased re-soaking of floodplain soils and floodplain aquifers
• Greater recharge of regional aquifer
• Greater plant growth during the dry season
Possible Effects of Climate Change on Riparian Ecosystems
Decreased precipitation• Decreased flooding and establishment of riparian
trees (but greater vulnerability to erosive floods)
• Decreased re-soaking of floodplain soils and aquifer
• Decreased recharge of regional aquifer
• Lower plant growth during the dry season
• With higher temp, greater stress on riparian ecosystems
• Channel drying and shifts to drought tolerant species (e.g., mesquite, saltcedar)
Changes in Rainfall are Uncertain
-400
4080
120160200
winter spring summer autumnSeason
Prec
ipita
tion
(mm
)
Current Hadley Canadian NCAR
Projected Precipitation Changes at Tombstone by 2060 (SRAG 2000)
Projected Temperature Changes at Tombstone by 2060 (SRAG 2000)
0
5
10
15
20
25
30
winter spring summer autumnSeason
Deg
rees
C
CurrentHadley ModelCanadian ModelNCAR Model
0
5
10
15
20
25
30
winter spring summer autumnSeason
Deg
rees
C
CurrentHadley ModelCanadian ModelNCAR Model
Warmer Temperatures are Likely
Hadley Center ModelCanadian Climate Centre ModelNCAR Regional Model
0
1
2
3
4
5
6
Winter Spring Summer Fall
Season
Deg
rees
C
Projected Changes in Mean Temperature by 2060 (SRAG 2000)
Warmer Temperatures are Likely
Hadley Center ModelCanadian Climate Centre ModelNCAR Regional Model
Season
Projected Changes in Daily Rainfall by 2060 (SRAG 2000)
-1.5
-1
-0.5
0
0.5
1
1.5
2
mm
/day
Winter Spring Summer Fall
-
1
-
Changes in Rainfall are Uncertain
Riparian pioneer plants (e.g., cottonwood, willow) depend on flows to disperse seeds and establish on open, moist sediment bars.
•• Large, long duration winter/spring Large, long duration winter/spring floods move and deposit sediment, floods move and deposit sediment, preparing bare surfaces suitable for preparing bare surfaces suitable for seedling growthseedling growth
•• Slowly receding spring floods Slowly receding spring floods deposit seeds and provide moisture deposit seeds and provide moisture for growthfor growth
Cottonwood and willow establish after Cottonwood and willow establish after winter/spring floods of appropriate size winter/spring floods of appropriate size and timingand timing
0
5
10
15
20
25
30
35
Mea
n da
ily fl
ow (m
3 /s)
ON
DJ
FM
AM
JJ
AS
Month
1987
1988
1989
1990
1992
1994
Non-recruitment years
0
5
10
15
20
25
30
35
Mea
n da
ily fl
ow (m
3 /s)
ON
DJ
FM
AM
JJ
AS
Month
1987
1988
1989
1990
1992
1994
Non-recruitment years
0
5
10
15
20
25
30
35
Mea
n da
ily fl
ow (m
3 /s)
ON
DJ
FM
AM
JJ
AS
Month
1987
1988
1989
1990
1992
1994
Non-recruitment years
0
5
10
15
20
25
30
35
Mea
n da
ily fl
ow (m
3 /s)
ON
DJ
FM
AM
JJ
AS
1991
1993
1995
Recent cottonwood recruitment years
0
5
10
15
20
25
30
35
Mea
n da
ily fl
ow (m
3 /s)
ON
DJ
FM
AM
JJ
AS
1991
1993
1995
Recent cottonwood recruitment years
Effects of Cattle Removal
1984
1998
Following cattle removal in 1988…
• Expansion of riparian vegetation
• Channel narrowing & stabilization
Photos by BLM
View from Hereford Bridge
San Pedro River, Arizona, National Geographic Magazine
•• Filter, bufferFilter, buffer–– Protect aquatic resources from pollutionProtect aquatic resources from pollution
Ecological Importance of Ecological Importance of Riparian ZonesRiparian Zones
•• CorridorCorridor–– organism movements, population viabilityorganism movements, population viability
•• BiodiversityBiodiversity–– high diversity of species and habitatshigh diversity of species and habitats–– ““green ribbongreen ribbon”” across arid landscapesacross arid landscapes