Transcript 150 years of land cover and climate change impacts on streamflow

150 years of land cover and climate change impacts
on streamflow in the Puget Sound Basin,
Washington
Dennis P. Lettenmaier
Lan Cuo
Nathalie Voisin
University of Washington Climate Impacts Group
Climate and Water Forecasts for the 2009 Water Year
October 6, 2009
Outline
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Background
Study area
Methods
Historical and projected results
Conclusions
Background
• Surface hydrology studies streamflow, soil moisture, snow,
evapotranspiration, etc.
• These variables are related to our drinking water and vegetation
water consumption.
• Human activities are also affecting land cover, e.g., urbanization,
deforestation, agriculture expansion.
• IPCC (2007) stated that climate change is most likely due to
human activities.
• All these will affect surface hydrology by changing mechanisms
like surface energy balance, surface infiltration capacity, snow
rain partition, etc.
Objective
1. How do land cover and climate change affect
streamflow?
Study area
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•
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Puget Sound Basin, Washington
State, USA
Temperate marine climate,
precipitation season: October March
Snow in highland. Not much in
lowland
Model
• Distributed hydrology-soil-vegetation model (DHSVM)
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
Interception
Evapotranspiration
Snow accumulation and melt
Energy and radiation balance
Saturation excess and
infiltration excess runoff
 Unsaturated soil water
movement
 Ground water recharge and
discharge
 Nature-urban mixed
hydrological process
Forcing data: temperature, relative humidity, wind speed,
incoming shortwave and longwave radiation and precipitation.
Historical and current land cover in Puget Sound
2002 land cover
Puget Sound Basin, Washington State
Map adopted from Alberti et al. (2004)
1883 land cover Reconstructed historical
land cover map (USGS 1883) using ArcGIS
(ArcMap, ArcInfo)
Climate data – Historical in Puget Sound (HCN stations)
Tmin has
stronger
increasing
trend than
tmax at some
locations
Model calibration and validation
Model calibration – urban basins in Puget Sound
DHSVM calibration at
hourly time step in
urbanizing basins
Land cover change effects on seasonal flow
Highland
Intermediate
elevation
Lowland
Intermediate
elevation
Land cover change effects on peak flow
Land cover change induced streamflow changes in
Puget Sound
Results of Mann-Kendall trend analysis on measurement and model
residual of annual maximum flows and annual flows. Trends are in % over
period of record, trend test is two-sided
USGS
gage IDs
Start date
End date
Annual maximum
flows
Annual flow
p
Trend
p
Trend
12115000
1945-10-1
2006-9-30
-
-402.3*
-
-45.5
12054000
1938-7-1
2006-9-30
<0.1
49.7
-
17.9
12056500
1924-10-1
2006-9-30
<0.05
36.7
<0.05
16.5
12133000
1922-10-1
1982-9-30
-
3.2
-
-28.0
12161000
1928-10-1
1980-9-30
-
32.0
-
-65.5
12120000
1955-10-1
2006-9-30
<0.01
163.1
-
17.9
Minimum detectable trend is greater than 500%.
Seasonal streamflow change in Puget Sound
Trend analysis results of measurement and model residual for seasonal
flows. Trend test is two-sided; trends are in % over period of record.
Fall (SON)
Winter (DJF)
Spring (MAM)
Summer (JJA)
Gages
p
Trend
p
Trend
P
Trend
p
Trend
12115000
-
-53.6
-
-21.1
-
-45.9
<0.05
-65.7
12054000
-
54.0
<0.05
100.5
-
6.4
-
-43.5
12056500
-
20.3
<0.05
30.7
-
10.7
-
-9.6
12133000 -
23.4
-
-45.7
<0.05
-87.9
-
77.6
12161000
-
-96.6
-
-12.4
-
-76.7
-
-25.5
12120000
<0.01
51.6
-
24.8
<0.1
23.7
<0.01
42.1
Urban site (12120000) has increasing trends consistent with model
simulation, annual maximum flow increases, summer flow decreases.
Historical temperature change effects
1915 condition
2006 condition
Temperature change effects – Historical
Historical land cover and climate change comparison
Land change
impacts
dominates in
lowland
Lowland
Intermediate
elevation
Highland
Historical land cover and climate change
comparison
Projected land cover change in Puget Sound in 2027 and 2050
2027 map was from Hepinstall et al (2008). 2050 map was from the population and urban
land cover regression for the lowland, and upland land was assumed to have no changes
compared to 2027 map.
Projected future climate change: GCMs, delta approach
Models
Institutions
CGCM 3.1 t47 Canadian Center for Clim ate Modelli ng and
Analysis Canada
CGCM 3.1 t63 Canadian Center for Clim ate Modelli ng and
Analysis Canada
CNRM_CM3 Centre National de Recherches Meteorologiques
France
ECHAM5
Max-Planck-Institut for Meteorology Germany
HADCM
Met Office, UK
HAD GEM1
Hadle y Center Global Environment M odel, v 1., UK
IPSL_CM4
IPSL (Institute Pierre Simon Laplace), Paris, France
BCCR
Bjerknes Centre for Clim ate Research Norrway
CCSM3
National Centre for Atmospheric Research USA
CSIRO_3_5
Australia's Commonwealth Scientific and Industrial
Research Organisation Au stralia
ECHO_G
Meteorological Institute, University of Bonn,
Germany
Meteorological Research Institute of KMA, Korea
Model and Data Groupe at M PI-M, Germany
FGOALS_0_G Institute of Atmospheric Physics China
GFDL_CM2_0 Geophy sical Fluid Dynamics Laboratory USA
GFDL_CM2_1 Geophy sical Fluid Dynamics Laboratory USA
GISS_AOM
Goddard Institute for Space Studies USA
GISS_ER
Goddard Institute for Space Studies USA
INMCM3_0
Institute for Numerical Mathematics Russia
MIROC _3.2
National Institute for Environmental Studies Japan
MIROC 3_2_hi National Institute for Environmental Studies Japan
PCM1
National Centre for Atmospheric Research USA
Run Simulation
Periods
1 2001-2098
1 2001-2098
1 2001-2098
1
1
1
1
1
1
1
2001-2098
2000-2098
2000-2098
2000-2098
2000-2098
2000-2098
1 1999-2098
2
1
1
1
2
1
1
1
1
2000-2098
2001-2098
2001-2098
2001-2098
2004-2098
2001-2098
2001-2098
2001-2098
2000-2098
Future climate conditions A1B scenario
Monthly Deltas = 2035-2065 vs. 1970-2000
Mon
1
2
3
4
5
6
7
8
9
10
11
12
Prcp
1.13
1.09
1.11
1.14
1.17
0.94
0.74
0.79
0.95
1.15
1.19
1.17
T
2.53
2.31
2.12
2.03
2.10
2.32
3.13
3.09
2.55
2.05
2.00
2.49
8
9
10
Prcp (mm)
400
350
prcp_obs
300
prcp_fut
250
200
150
100
50
0
1
2
3
4
5
6
7
Month
11
12
Tmax (C)
30
25
tmax_obs
20
tmax_fut
15
10
5
0
1
2
3
4
5
6
7
8
9
10
11
12
Month
14
tmin_obs
tmin_fut
12
Tmin (C)
10
8
6
4
2
0
-2
1
2
3
4
5
6
7
-4
-6
Month
8
9
10
11
12
Projected climate change impacts on runoff and centroid
Delta
approach,
2050s
climate
vs. 1970 2000
climate,
and 2002
land.
Day starts
from Oct.
1 to
Sept.30
Projected land cover change impacts on runoff
2002 and
2050 land
covers
and 2050s
climate
Projected climate and land cover change impacts on
mean annual total runoff
<500m
500m - 1000m
1000m - 1500m
>1500m
Land 2002, 1970 2000 Climate (mm): a
822
890
595
453
Land 2002, 2050s
Climate (mm): b
759
819
611
508
Land 2050, 2050s
Climate (mm): c
914
1030
396
262
Climate Change (%)
Compare a vs. b
-8
-8
3
12
Land Change (%)
Compare b vs. c
20
26
-35
-48
Conclusions
• Upland basin mean flow sensitivity to land cover change is
mostly as a result of changes in snow accumulation and
ablation, and lower ET associated with reduced vegetation.
• However, overall upland basin seasonal flows distribution,
especially in the transient snow zone, are much more
sensitive to temperature change effects – both to mean and
peak flows – than to land cover change
• Lowland basin mean flows are much more sensitive to land
cover change than are upland basins, especially in the
most urbanized basins.
• Future runoff is projected to increase primarily in the
upland basins (above 1000 m). Runoff centroids will move
earlier in the year in the upland basins, especially with
elevation above 1500 m. The higher the elevation, the larger
the forward shift in centroid.
• Projected land cover change impacts occur across all
elevation zones. Land cover change will tend to increase
runoff at lower elevations, but decrease runoff at higher
elevations, mostly due to urbanization at low elevation, and
forest regrowth at higher elevations. Land cover change
does not affect runoff timing in a consistent way because
land cover change impacts mostly are on
evapotranspiration rather than snow.