Transcript Results: Impacts to Demand

THE IMPACT OF CLIMATE
CHANGE ON WATER
SUPPLIES
Jim Doane PE
Spring 2004
Order of Presentation
• What is Current
– Unprecedented issues for water supply planning
– There will be temperature changes as a result of
human activity
– How these changes impact the hydrology of the
Pacific Northwest
– How these changes impact the Bull Run Water
System
Order of Presentation
• What is emerging
– Worst case Pentagon Study on Climate Change
(Leaked to British Press in Feb 2004)
• Collapse of the Atlantic Ocean’s thermohaline
circulation
–
–
–
–
Caused by Global Warming
Change in years instead of decades as presently predicted
Vast climate changes---both globally and locally
Colder, windier and drier and shorter growing season in
the Northeast US. Less productive agriculture.
Order of Presentation
– A longer growing season in the Southwest US. More
productive agriculture if water can be provided.
– Increased competition for water leading to international
conflict.
– http://www.ems.org/climate/pentagon_climatechange.pdf
Planning for Water Supply
• Based on historical values
– Demand….present demand plus growth
(generally population based)
– Supply
• Historical Record
• The longer the record, the higher the confidence
• But the Past is no longer a good precursor
of the future
TEMPERATURE CHANGES
• From 2001 Work by the University of
Washington
• Dr. Philip Mote of the JISAO Climates
Impacts Group
Assessments of Climate Change
• Thousands of peer-reviewed papers
• Peer-reviewed assessment:
Intergovernmental Panel on Climate Change
(IPCC)
• Major reports in 1990, 1996, 2001
• National Academy of Sciences panel, 2001
underscored IPCC conclusions
Humans will keep
increasing CO2
• carbon dioxide
concentration has increased
by ~32%
• the carbon budget: nature
has absorbed roughly half
our emissions
• there is no question that
the increase is unnatural
• from a very long term
perspective, these changes
are enormous
Evidence that Earth is Warming
• Thermometers show warming of 0.4-0.8°C (0.7-1.4°F)
since 1900
• Arctic permafrost is melting
• Worldwide, most glaciers melting
• Arctic ice thinning
• Spring coming earlier (snow cover; blooming, leafingout dates)
• Borehole temperatures indicate warming
• But: not every station shows warming; upper-air
temperatures not increasing (satellites, balloons)
Global average temperature
degrees Celsius
0.8
0.4
0
-0.4
-0.8
1860
1880
1900
1920
1940
1960
1980
2000
Some Evidence that Humans are
Responsible
• Rate of warming unusual
• Hard to explain as natural (volcanoes, solar,
ocean)
• Pattern of warming (and stratospheric cooling)
consistent with human influence
The earth is warming -- abruptly
Natural Climate Influence
Human Climate Influence
All Climate Influences
Projections into the Future
• Projections of future greenhouse gases
(depends on socioeconomic projections)
• Climate models: different “sensitivity”
• Wide range of estimates: 1.4-5.8°C (2.510.4°F) by 2100, faster than any time in at
least 10,000 years.
• Estimates show Pacific Northwest will
increase by 3-5°F by 2040.
Temperature trends in the PNW
• Almost every
station shows
warming (filled
circles)
• Urbanization not a
major source of
warming
PNW average temperature
warmest scenario
average
coolest scenario
observed
CGCM1
19
20
s
19
40
s
19
60
s
19
80
s
20
00
s
20
20
s
20
40
s
0s
54
53
52
51
50
49
48
47
46
45
44
19
0
Degrees F
Northwest warming
Temperature Change Conclusions
• The bulk of the evidence points to a human
influence on climate, with a global warming
of 2.5-10.4F likely in the next 100 years.
• Regional warming likely to be faster than
average global warming (3-6°F by 2040s);
main vulnerability: reduced snow leading to
summer water shortages
Implications for Water
Management
• 2001 Work by University of Washington
• Alan Hamlet, Andy Wood and Dennis
Lettenmaier of the JISAO Climates Impacts
Group
(mm)
Winter
Precipitation
Summer
Precipitation
Hydrologic Characteristics of PNW Rivers
Normalized Streamflow
3.0
2.5
Snow
Dominated
2.0
Transient Snow
1.5
Rain Dominated
1.0
0.5
0.0
10 11 12 1
2
3
4
Month
5
6
7
8
9
Sensitivity of Snowmelt and Transient Rivers
to Changes in Temperature and Precipitation
9 0000 0
7 0000 0
6 0000 0
5 0000 0
4 0000 0
3 0000 0
2 0000 0
1 0000 0
19 74
1 974
1974
1974
19 74
1 974
1974
1974
197 4
197 4
197 3
1973
1973
19 73
19 73
0
197 3
•Streamflow timing is altered
• Annual volume stays about
the same
8 0000 0
Flow (cfs)
Temperature warms,
precipitation unaltered:
Water Year
9 0000 0
8 0000 0
6 0000 0
5 0000 0
4 0000 0
3 0000 0
2 0000 0
1 0000 0
197 4
197 4
197 3
1973
1973
19 73
19 73
0
197 3
•Streamflow timing stays about the same
•Annual volume is altered
7 0000 0
Flow (cfs)
Precipitation increases,
temperature unaltered:
Water Year
Effect of 1992 Winter Climate on Two PNW Rivers
1200
1000
Flow (cfs)
(caused predominantly by
warm temperatures)
800
1992
600
avg
400
200
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
Dec
Oct
0
Nov
Cedar River
Western Cascades
600000
400000
1992
300000
avg
200000
100000
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
Dec
Nov
0
Oct
(caused both by warm
temperatures and
decreased precipitation)
500000
Flow (cfs)
Columbia River
at The Dalles
Changes in Mean
Temperature and
Precipitation from
GCMs
VIC
Hydrology Model
ColSim
Reservoir
Model
Climate Change Scenarios 2020s
Climate Change Scenarios 2040s
The main impact: less snow
April 1
Columbia
Basin
Snow
Extent
Columbia River at The Dalles
2020s “Middle-of-the-Road” Scenario
600000
500000
400000
Base
300000
comp 2020
200000
100000
aug
jun
apr
feb
dec
0
oct
Average Flow (cfs)
DALLES
Columbia River at The Dalles
2040s “Middle-of-the-Road” Scenario
600000
500000
400000
Base
300000
comp 2040
200000
100000
aug
jun
apr
feb
dec
0
oct
Average Flow (cfs)
DALLES
Water Resources in the Columbia River Basin
System objectives affected by winter flows
Winter hydropower production (PNW demand)
System objectives affected by summer flows
Flood control
Summer hydropower production (California demand)
Irrigation
Instream flow for fish
Recreation
100
95
90
Current Climate
2020s Scenario
2040s Scenario
85
80
75
70
Lake Roosevelt Recr.
Snake Irrigation
Main Stem Fish Flows
Snake Fish Flows
Non-Firm Energy
Firm Energy
65
Flood Control
Re liability of Objective (%)
Simulated Reliability of Water Resources Objectives
for “Middle-of-the-Road” Scenarios
1 Palisades
2 Milner
3 Oxbow
4 Ice Harbor
5 Kiona
5 4
3
1
2
Snake River at Milner
18000
16000
14000
Flow (cfs)
12000
base
comp 2020
comp 2040
10000
8000
6000
4000
2000
0
O
N
D
J
F
M
A
M
J
J
A
S
Snake River at Ice Harbor
140000
120000
Flow (cfs)
100000
base
comp 2020
comp 2040
80000
60000
40000
20000
0
O
N
D
J
F
M
A
M
J
J
A
S
Yakima River at Kiona
14000
12000
Flow (cfs)
10000
base
comp 2020
comp 2040
8000
6000
4000
2000
0
O
N
D
J
F
M
A
M
J
J
A
S
General Conclusions for the PNW
PNW hydrology is predominantly controlled by winter conditions in
the mountains. Warmer temperatures produce streamflow timing
changes in most PNW basins. Changes in precipitation produce
changes in streamflow volumes. Basins encompassing the midwinter snow line are most sensitive to warming. Basins at high
elevations with cold winter temperatures are less sensitive.
The primary impact of warming in the PNW is loss of mountain
snowpack. For the scenarios investigated, both warm/wet and
warm/dry scenarios result in decreased snow water equivalent in the
Columbia basin.
Warmer temperatures generally results in higher winter flows, lower
summer flows, and earlier peak flows
Effects to the Columbia water resources system are largely
associated with reduced reliability of system objectives affected by
summer streamflows (water supply, irrigation, summer hydropower,
instream flow).
General Conclusions for the PNW (cont.)
There are significant uncertainties regarding changes in
precipitation and the resulting intensity of reductions in summer
streamflows and increases in the frequency of droughts.
However, a consistent and robust result is that some reduction in
summer streamflow and increase in drought frequency is present in
all scenarios by the 2040s for the Columbia basin.
The greatest impacts to the Columbia system are for the warm/dry
scenarios, which produce the strongest reductions in summer
streamflows and the greatest increases in drought frequency.
The reductions in summer streamflows in these scenarios are likely
to exacerbate existing conflicts over water, the impacts of regional
growth, and weaknesses in infrastructure, water management
practice, and management institutions.
The Impacts of Climate Change on
Portland’s Water Supply
Work by Joe Dvorak, Dennis Kessler, Azad Mohammadi
Portland Bureau of Water Works
Richard Palmer, Margaret Hahn
UW Dept of Civil Engineering
Climate Impacts Group, JISAO
Spring 2002
Objectives Of Study
Examine the impacts of climate change on
the Bull Run Watershed:
• Bull Run Watershed hydrology
• temporal and spatial analysis
• Forecasted M&I demand
• System performance
Portland’s Water Supply System
•
•
•
•
•
Serves ~ 840,000 people
Largest system in state; serving since 1895
42 BG annual demand
115 MGD average daily demand
Bull Run Watershed
– Dam No.1 (10 BG)
– Dam No.2 (7 BG)
Bull Run Watershed
•
•
•
•
•
•
107 square miles
2350 feet elev.
Rainfall driven
80 in./yr. rainfall
170 BG/year yield
Peak Snowpack:
– 16 inches Snow Water Equivalent (SWE)
• Snowmelt typically occurs before June
Methodology
Three sets of models used in the study:
Four Global Circulation
Models
Hydrological Model
WaterSupply Model
Predicts changes to temperature and
precipitation based on altered CO2
concentration.
Uses GCMs to predict climate
impacted runoff in watershed.
Forecasts system performance based
predicted watershed hydrology.
Results: Impacts to Climate
•
Average warming trends of ~1.5 OC for the 2020
decade and ~2 OC by 2040.
•
Increased winter precipitation, with less snowfall,
but more rain
•
A decrease in late spring and summer precipitation
Results: Impacts to Temperature
Temperature Change
for Climate Change Scenarios
4
2020 Climate Change
2040 Climate Change
3.5
Degrees C
3
2.5
2
1.5
1
0.5
0
Oct Nov Dec Jan Feb Mar Apr May Jun
Jul Aug Sep
Results: Impacts to Snowfall
Results: Impacts to Precipitation
Precipitation Fraction for
Climate Change Scenarios
1.2
2020 Climate Change
2040 Climate Change
Fraction Precipitation
1.15
1.1
1.05
1
0.95
0.9
0.85
0.8
Oct Nov Dec Jan Feb Mar Apr May Jun
Jul Aug Sep
Results: Impacts to Hydrology
•
Average winter streamflows increase by 15%
•
Late spring streamflows decrease by 30% due to
spring snowmelt being non-existent
•
50 percent of the time, April to September flows
may decrease by as much as 12.9 BG
•
Less impact to storage (0.1 - 3.6 BG) depending
on drawdown timing (avg. 1.3 BG)
Results: Impacts to Streamflow
Results: Impacts to Streamflow
(April to September)
100
Total Streamflow (Billion Gallons)
90
80
Current Climate
70
2040 Climate (average)
60
50
40
30
20
10
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Exceedance Probability
0.7
0.8
0.9
1
Results: Impacts to Demand
•
Water demands shown to be less sensitive to
climate change than hydrology
•
8% increase in 2040 drawdown demand
•
4% increase in 2040 average annual demand
Results: Impacts to Demand
2040 Forecasted M & I Demand (includes conservation)
30-day Moving Average
300
275
No Global Warming
Average Climate Change
225
200
175
150
Date
12/27/82
11/27/82
10/28/82
9/28/82
8/29/82
7/30/82
6/30/82
5/31/82
5/1/82
4/1/82
3/2/82
100
1/31/82
125
1/1/82
Demand (mgd)
250
Results: Impacts to Drawdown
Impacts to drawdown length will vary
from year to year:
 Historical extreme years like 1987 change little,
however, the frequency of these years increases.
 Drawdown length for average years may increase by as
much as 60 days, as drawdown starts earlier due to
early spring recession.
Results: Impacts to System
•
On average, the combined effect of climate change
on hydrology and demand may increase storage
requirements by 2.8 BG.
•
Global warming will push forward the need to
provide more sources of supply in the future
Impacts to Bull Run Watershed
Impacts to Overall System
Summary
•
Warming trends of 1.5 OC (up to 3.5 OC) for 2020 and 2.0 OC (up to 4.5
OC)
•
by 2040.
Average winter precipitation will increase, late spring runoff will
decrease, spring snowmelt may be non-existent.
•
Streamflows in the summer will decrease.
•
The impacts on hydrology may increase storage requirements by 1.3 BG
(up to 3.6 BG)
•
Demands will increase by 1.5 BG (up to 2.4 BG)
•
The effect of climate change on hydrology and demand, will increase
storage requirements by 2.8 BG (up to 5.4 BG)
Conclusions
•
Assessing climate change impacts will be vital in
future water supply planning.
•
Climate change is only one factor in long-term
planning. Other factors will include:
– Future demands (due to growth and/or service area
changes)
– ESA (fish flow releases)
– Conservation Programs, investments & success
The Future
• JWC has a similar study underway now
– JWC supplies Hillsboro, Beaverton, Forest
Grove and TVWD
• Results are expected this summer
• Expect results to be similar to Bull Run
• Vector Issues
Impact of the Emerging Data
• We have only the summary of the leaked
Pentagon Study
– We don’t yet have the necessary specifics
• To evaluate its validity or likelihood
• To anticipate what impact the loss of the Atlantic
termohaline circulation will have on the Pacific
Northwest
• To see how much this throws off the information I
have presented today.
The Engineering Community
• Meeting with other engineering working on
climate change issues.
–
–
–
–
Providing information
Trying to educate other engineers
Trying to educate the public at large
Trying to educate elected officials
Acknowledgements
• The slides showing the impacts of
temperature change are by Dr. Philip Mote
of the JISAO Climates Impacts Group.
• The slides showing the impacts on water
resources are by Alan Hamlet, Andy Wood
and Dennis Lettenmaier of the JISAO
Climates Impacts Group.
Acknowledgement Cont.
• The slides on the Portland Study are by
Richard Palmer, Margaret Hahn
of the JISAO Climates Impacts Group.
• Assisting my understanding of the issues of
Portland’s water supply were Joe Dvorak,
Dennis Kessler, Dr. Azad Mohammadi of
the Portland Water Bureau