Climate Change in the US Southwest: Mitigation and Adaptation

Climate Change in the US Southwest: Mitigation and Adaptation

II Seminario Internacional “Evidencias y Contradicciones del
Cambio Climático: Mitigación e Impacto”
Centro Tecnológico de Hidrología Ambiental, Universidad de
Talca
Climate Change in the US
Southwest: Mitigation and
Adaptation
Juan B. Valdés1,2
Department of Hydrology and Water Resources, The University of
Arizona, Tucson, AZ 85721, USA
2International Center for Integrated Water Resources
Management (ICIWaRM), a UNESCO Level II Center
IPCC: “Climate change will intensify the
hydrologic cycle”
changes in
averages/ trends
changes in variability
(magnitude, severity, duration)
2
Water challenges in arid and semi-arid regions
Extent of regions: One-third of earth’s land surface is
semi-arid or arid.
Population growth:
• The most rapidly growing countries are concentrated
in these arid regions; and
• Population pressures and development are drying up
rivers or leaving water unfit for most uses.
Nonsustainability: In response, water users have
tapped regional aquifers, resulting in overdraft and
saltwater intrusion, causing reliance on nonsustainable water supplies.
3
US Southwest: It is Dry!
4
Parallel challenges in U.S. Southwest
Extent of regions: one-quarter of U.S. is semi-arid
Population growth:
• The most rapidly growing states are the most waterscarce
• Dams, diversions, and over-allocation of surface
waters have dried up many rivers, and left others
polluted
Nonsustainability: vast numbers of wells tap regional
aquifers, resulting in overdraft, subsidence, salinity,
non-sustainability
Plus drought: Large portions of southwest US have
been in drought most of the last decade and
5
CLIMATE CHANGE
US Southwest: Water Scarcity
• Scarcity has driven and changed water
law in the US Southwest
• “every drop of water should be used”
• Reclamation Act, 1902 USBR
• Colorado River Example: water totally
appropriated.
– Water quality issues
– Overuse of appropriation by California
– Colorado Delta
– Imperial Valley
6
Courtesy of John Dohrenwend
Climate
Variability
and Change
June 2002
Courtesy of John Dohrenwend
There is significant
variability in the main
sources of water in the
region. The main
challenge is to
separate them.
April 2003
7
Lake Powell
Climate Challenges in US
Southwest
•
•
•
•
US Southwest
Colorado River Basin
The State of Arizona
Tucson Metropolitan Area
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Climate Change Impact on SW Snowfall
• High dependence on snowmelt in spring: Approximately 85%
of the water for human use in the Rocky Mountain region comes
from spring snowmelt. Snow accumulations are one of the most
useful predictors of stream flow and water resource availability in
the Colorado Basin.
• Climate change is threatening the snow reservoir
• Approach: Evaluate snowfall for the period 1968-2079 for three
different latitudinal bands and seven altitudinal bands using:
– 926 observations (227 for SNOTEL Stations and 699 for TD3200 stations) are
collected for validation of the model simulation.
– WRF( Weather Research Forecast) regional climate model was to
downscale the UKMO-HadCM3 A2 for the period 1968-2079.
– Statistically downscaled results from 16 GCMs to evaluate uncertainty
(Wi et al, WRR 2012)
9
Movement of 0° Isothermal Elevation
Latitudinal and altitudinal location of the region of zero degree mean winter
(Dec-Mar) temperature for the three study periods, superimposed on the
contours of the linear trend in winter (Dec-Mar) snowfall over the 19692079 period
FINDING: The regions of
strongest declines in snowfall
roughly correspond to the
region of migration of the zero
degree Celsius line
(Wi et al, WRR, 2012)
10
Example: Colorado River Basin
Colorado river allocations:
Upper basin: 7.5 MAF (9300 Hm3)
Lower basin: 7.5 MAF (9300 Hm3)
Mexico:
1.5 MAF (1900 Hm3)
Total
16.5 MAF (20350 Hm3)
(NRC, 2007)
(USGS, 2004)
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Allocation of Colorado Water
Reconstruction of Colorado River at Lees Ferry, 1490-1997
Woodhouse et al., 2006
12
Impact on Colorado River Uses
• Loss of riparian habitat
• Groundwater depletion
• Land subsidence
55 PPM
Colorado River Flow Below All Major Dams and Diversions
30000
Discharge (1000 acf)
25000
20000
15000
10000
5000
0
800 PPM
Year
13
Disappearance of Riparian Habitat
1940
1975
Santa Cruz River’s Riparian Habitat
14
Colorado River Vulnerabilities
15
(US Bureau of Reclamation, 2012)
Mismas Tasas de Transpiración,
Temporada Más Larga
Riparian and Pan ET: Decadal Averages
12
2001-2010 Riparian
2051-2060 Riparian
2091-2100 Riparian
2001-2010 Pan ET
2051-2060 Pan ET
2091-2100 Pan ET
10
ET (mm/day)
8
MPI model
A1B scenario
6
4
2
0
0
50
100
150
200
250
300
350
Day of Year
Serrat-Capdevila et al JH (2009)
16
The State of Arizona: The Three C’s
Since the 1950’s,
Southern Arizona’s
economy was based
on:
• Copper mining
• Cotton
• Climate
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Climate attracts people, who use water
Southern Arizona’s climate attracted:
• military bases & aerospace industry
• retirees and asthmatics
• resorts, spas, dude ranches
As a result, the population exploded, and each person
consumed an average of 200 gallons per day.
Limited surface water supplies were fully utilized, and
turbine wells were used to pump groundwater.
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Arizona Water Resources History
• 20th Century
•Development
followed existing
supplies
•21st Century
•Supplies following
existing development
•Importation & Transfers,
CAP,Groundwater
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Phoenix Population Growth
Phoenix Area Land Change
1975
1955
1934
1995
1912
Phoenix
Urban
Agriculture
Source: CAP-LTER, Arizona State University
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Managing the Extremes Phoenix Water Supply
= 3 million
Metropolitan Phoenix
20
1993 -2.25 year supply
15
10
2000 - 3 month supply
Water
Snow Depth
5
0
Oct
Nov
Dec
Jan
Feb
Mar Apr
Month
May
Jun
Jul
Aug
Sep
Salt-Verde Watershed Snowfall Volume
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Análisis de Sequías: Verde Basin
SPI (Indice Estandarizado de Precipitación, Kerr 1993)
Period 1950-2100
3 months
12 months
24 months
22
(Serrat-Capdevila et al., AGU 2010)
Análisis de Sequías: Verde Basin
SPI: Standarized Precipitation Index
Droughts in SPI12
-2.1
-2
-2.2
-2.1
-2.3
-2.4
-2.5
-2.6
Period 1950-99
Period 2000-49
Period 2050-99
-2.1
-2.2
-2.3
-2.4
10
20
30
40
50
-2.7
0
5
10
15
20
25
-2.7
5
10
15
20
Number of Events
Droughts in SPI12
Droughts in SPI24
16
14
10
2.2
0
Number of Events
12
2.4
12
Duration
1.8
1.6
Duration
8
2
6
4
1.4
10
8
6
4
2
1.2
1
-2.4
-2.6
Droughts in SPI03
2.6
-2.3
Las sequías serán más
intensas y de mayor duración
en la cuenca del río Verde
-2.6
0
-2.2
-2.5
Number of Events
Duration
-2
-2.5
-2.7
-2.8
Droughts in SPI24
-1.9
Intensity (SPI)
-1.9
Intensity (SPI)
Intensity (SPI)
Droughts in SPI03
-2
0
10
20
30
Number of Events
40
50
0
2
0
5
10
15
Number of Events
20
25
0
0
5
10
15
Number of Events23
(Serrat-Capdevila et al., AGU 2010)
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Mitigation and Adaptation
• Mitigation actions have been difficult due
to the political climate. However there are
hopeful signs e.g. increased reliance on
natural gas, increased efficiency
regulations on automobiles and other
emitters, clean air regulations for fossil
power plants, etc.
• Adaptation measures have been more
widespread and some examples in the US
Southwest and the Tucson metropolitan
area will be presented here.
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Tucson Metropolitan Area
•Adaptation Measures to Dwindling Water
Supplies in Tucson AMA
•Impact of Conservation Measures
•Challenges to Water Conservation
•Tucson AMA transition to more “sustainable”
water supplies
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Responses to dwindling water supply
In the 1970s, Tucson responded to its lack of
surface water and declining groundwater table by:
• buying & retiring cotton farms
• raising price of water and instituting conservation programs
• treating & delivering effluent to irrigate golf courses & parks
In the 1980s, State of Arizona passed a Groundwater
Management Act that:
• forbid new farms and severely restricted new wells
• imposed mandatory conservation on farms, cities, golf courses
• encouraged use of imported Colorado River water
• but left copper mines alone, because the industry appeared doomed
The water problem appeared to be under control.
26
Unanticipated events challenge water managers
The 1990s saw a number of surprises that
increased water demand and decreased
available supplies:
• population in Arizona grew even faster than forecast
• public grew suspicious that water conservation encouraged
growth
• treated Colorado River water destroyed pipes, looked &
smelled bad
• new technology revived the copper mining industry
• purchase & retirement of farmland stopped
AND demand characteristics changed
27
…confronted the reality of urban water uses
…but
swimming
pools grew
in popularity
Dark blue dots represent residential lots with swimming pools in Tucson, AZ
28
Tucson AMA Adaptation Measures
•
•
•
•
Aquifer Recharge/Banking
Water Harvesting (local, storm collecction)
Reclaimed Water
Increased Efficiency and Monitoring of
Water Supply
• Outreach and Education
29
Reclaimed Water
Reclaimed Treatment/
Recharge Facilities
City of Tucson
30
Restoration of Riparian Areas
• Contain Critical
Habitat
• Support Native &
Migratory Species
• Slow Flood Flows
• Provide Erosion
Protection
• Improve Water
Quality
• Provide Recreational
Opportunities
• Count Towards ESA
Compliance
31
Storm Runoff Recovery
Sweetwater Wetlands Project
32
Tucson: Water Table Elevation Declines
WRRC
33
Impact of Conservation Measures
34
Impact of Increased Efficiency
35
It is not only LA
36
Challenges to Water Conservation
• “Hardening” of the demand giving less
flexibility to deal with water scarcity
• Loss of revenue for water utilities
• Reluctance of population that believe
water conservation will promote more
development
• Structural changes are more easily
accepted by population compared with
behavioral changes
37
Tucson: Transition to Renewable
Supplies
In 2013 pumping would be at 1945 level
38
Pending Challenges to Adaptation
• GCMs “are not ready for prime time”
• Climate change and its impact on AZ
junior rights on the Colorado River
• Competition between federally protected
rights (Native-American, ESA) and M&I
demands
• Demand for ecosystem services still not
fully resolved
39
Problem: competing demands on
limited resources
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Cuales son las medidas apropiadas?
Debido a esta gran incertidumbre el curso
de acción apropiado no debe ser inacción
hasta que se consiga más información pero
usar el principio cautelar (“non-regret
approach”), p.e. extender los datos usando
proxies, GCMs y “critical scenarios”
expander sistemas de alerta y detección,
construcción modular de obras hidráulicas
entre otras acciones
"Algunos dicen que es irrevocable, otros que es irreversible. Dada la
ausencia de consenso, sugiero que no hagamos nada drástico"
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Gracias por su atención
Para información adicional contactar:
Juan B. Valdés
[email protected]
The University of Arizona
www.hwr.arizona.edu
43
Photo: J. Overpeck