The title describes it all. Jeremy Pal's student Brianna Pagàn and coworkers put an impressive set of tools to estimate the impacts of land use and climate change on water resources of south California.

1. Projecting Climate Change Impacts on Water
Resources in Regions of Complex Topography:
A Case Study of the Western United
States and Southern California
Brianna Pagán1, Moetasim Ashfaq2, Deeksha Rastogi2,
Donald R. Kendall1, Shih-Chieh Kao2, Bibi S. Naz2, Rui Mei2
Jeremy S Pal1 <jpal@lmu.edu>
1. Loyola Marymount University, Dept of Civil Engineering and Environmental Science
2. Oak Ridge National Laboratory, Climate Change Science Institute

2. Western US Water Hydrologic Cycle Schematic
Precipitation
(when it falls)
Demand
(when we need it)Runoff
(when we get it)
Reservoirs store surplus water in the
spring for the summer when
demands are highest.
Large reservoirs store water during
periods of surplus to get us through
multi-year droughts.
75% of annual streamflow in California
is snowmelt.
In California, water in many
reservoirs is released in wintertime
for flood control purposes.
Climate change impacts on western
US hydrology is critical to our
understanding of future Southern
Californian water resources.

3. Where does Southern California get its water?
Local Supplies
Groundwater
Recycled Water
Conservation
Colorado River Aqueduct
Colorado River Basin
LA Aqueduct
Mono Lake
/Owens Valley
CA Aqueduct
Sacramento
River Basin
San Joaquin
River / Tulare
Lake Basins
California hosts world's largest, most productive, and most controversial
water system à 49 km3/yr, 30 million people, 2.3 million ha of irrigation.

4. Los Angeles Aqueduct (~7%)
Mono Lake and Owens Valley: 0.50 km3/yr
(16 m3/s), 674 km, Gravity
Owned by the Los Angeles Department of
Water and Power.
Owens Lake Mitigation – Dust Control
• Dry lake bed
• Largest source of dust pollution (PM-
10) in US.
• Human health risks
• Reduced 0.05 km3/yr (1.6 m3/s)
Mono Lake Decision (1982)
• Migrating and nesting birds
• Reduced 0.14 km3/yr (4.5 m3/s)

5. Colorado River Aqueduct (~25%)
California allocation
• 5.4 km3/yr (172 m3/s)
• Irrigation districts
• Metropolitan Water District of Southern
California (MWD): 55 m3/s, 389 km, 5
pumping stations, 492 m lift.
Modern Issues
• Over allocated by ~4.7 km3/yr (~150 m3/s)
• Rising populations in other states
Colorado River
• 19.7 km3/yr (625 m3/s) – ~2.7 Adige Rivers
• Serves 30 million people across seven
states – ~1/2 Italy

6. State Water Project (~30%)
Basins support 25 million people and
$36 billion agriculture industry
Modern Issues – Delta Smelt
• Indicator species for the overall
health of the Delta's ecosystem
• Endangered Species Act
• Delta Smelt Pumping restrictions
Originates from SRB and SJR-TLB in San
Francisco Bay Delta
Metropolitan Water District of Southern
California: 2.4 km3/yr (75 m3/s), 489
km, 6 pumping plants, 988 m lift
Hypomesus transpacificus / U.S. Fish
and Wildlife Service
http://www.water.ca.gov

7. Local Supplies (~38%)
Recycled Water
Groundwater including stormwater
capture
Conservation
Desalination

8. Objectives
Will climate change significantly modify the hydrologic cycle in the
Western United States?
If so, will it influence imported supplies in such a way that leaves
Southern California in periods of extended water shortages?
Are long-term plans for expansion of local supplies adequate enough
to meet any deficit brought on by climate change?

9. Greenhouse Gas Concentrations (0 - 2014)
IPCC 2007
500
750
1000
1250
1500
1750
2000
250
275
300
325
350
375
400
0 200 400 600 800 1000 1200 1400 1600 1800 2000
CH4(ppb)
CO2(ppm)N2O (ppb)
Year Data Source: NOAA
Carbon Dioxide (CO2) – 43% increase
Nitrous Oxide (N2O) – 21% increase
Methane (CH4) – 140% increase

10. -0.50
-0.25
0.00
0.25
0.50
0.75
1.00
1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Differnece from 1951-1980 (°C)
Global Surface Temperature Differences from 1951-1980
Warmer than Normal
Colder than Normal
2015
Data Sources: NASA (T) & NOAA (ENSO)
2016
Most of the warming has occurred in the past 50 years or so,
as have most of the anthropogenic greenhouse gas emissions.
• The 17 warmest years have occurred in the past 19 years.
• 1976 was the last cooler than normal year.

11. Temperature Trends (1901-2012)
IPCC 2013
°C
Temperatures in the Western US have increased by 1 to 2°C
over the past century, which is well above the global average.

12. Climate Models or Earth System Models
3D representations of the major components of the
Earth system: land surface, atmosphere, oceans, ice.
Used to simulate a variety of processes, such
as climate change, land cover change.

13. IPCC 2013
Climate Model Simulations of the Past (1900-2005)

14. IPCC 2013
Climate Model Simulations of the Past (1900-2005)

15. Climate Models / Earth System Models
Weather vs Climate Analogy: It is impossible to predict the age at which
someone will die; however, we can say with high confidence that the average
age of death in industrialized countries is about 75. Richard Somerville, Scripps
All models are wrong but
some are useful. George Box

16. 100
200
300
400
100
200
300
400
0100000200000300000400000500000600000700000800000
CO2 (ppm)
Years Before Present
100
200
300
400
500
600
700
800
900
1000
100
200
300
400
500
600
700
800
900
1000
0100000200000300000400000500000600000700000800000
CO2 (ppm)
Years Before Present
CO2 Concentrations from the Past 800,000 years (ice cores)
Pre-Industrial Anthropogenic Future
Current Level
CO2 in 2100
(business as usual)
2°C COP21 Minimum
Hoped For ”Paris” Pledge
3.5°C COP21 Current
”Paris” Commitment

17. Projected Global Surface Temperature Change
Spread indicates range
of possible futures.
Current
Temperature
Business as Usual
3 to 5.5°C
“Paris-Level” Mitigation
1 to 3°C
Projections of climate change in 2100 range from 1 to 5°C globally depending on
the greenhouse gas concentration scenario… About double over land.

18. Climate Change Impacts

19. Human Health
Agriculture
Water Resources
Ecosystems
Storm Surges
Regional Climate Model for Impacts Studies
Regional Climate Models (RCMs) can be “nested”
within an AOGCM in order to increase the resolution
(10s km) of a climate simulation.
Boundary conditions are obtained from the AOGCM.
Intended to enhance the AOGCM simulation.

20. Climate Change Projection Simulations
10 AOGCMs
1 High-Res RCM
1 Hydro Model
Impacts on
Water Resources
ACCESS
BCC-CSM
CCSM4
CMCC-CM
FGOALS
IPSL-CM5A-LR
MIROC5
MPI-ESM-MR
MRI-CGCM3
Nor-ESM1-M
RegCM4 16-km
VIC 4-km
Simulations performed on ORNL’s Titan – The fastest supercomputer in the US.
To date, the most comprehensive and highest resolution assessment.
Greenhouse Gas Concentrations:
Historical (1976-2005)
RCP 8.5 Future Scenario (2021-2050)

21. Hydrologic Model (VIC) Verification
Naz et al., 2016
Runoff
Calibration
(1981-2000)
Runoff
Validation
(2001-2008)
High Resolution Hybrid Modeling

22. -25 -15-75 -65 -55 -45 -35 -25 -15 -51.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0
Temperature (o
C)
a
Snow Depth (%)
b
E
Precipitation (mm/yr) Evapotranspiration (mm/yr) Runoff (m
Albedo (
c
Projected Changes (2021-2050 minus 1976-2005
Temperature and Snow Changes: 2021-2050 minus 1976-2005
Temperatures projected to increase
an additional 1.0 to 2.0°C by 2050.
• Higher than the global average.
The largest increases at projected at
higher elevations due to snow related
changes in surface albedo (reflectivity).
°C -25-75 -65 -55 -45 -35 -25 -15 -51.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0
Temperature (o
C)
a
Snow Depth (%)
b
Precipitation (mm/yr) Evapotranspiration (mm/yr) Run
Albe
c
Projected Changes (2021-2050 minus 1976-2
%
Up to 75% decrease1.0 to 2.0°C increase

23. Precipitation Changes: 2021-2050 minus 1976-2005
3 to 4% increase in precipitation, but with considerable intermodel uncertainty.
mm/yr

24. Precipitation Seasonality Changes: 2021-2050 minus 1976-2005
0.008 -0.004 0 0.004 0.008
Precipitation Seasonality
Changes (2021-2050 minus 1976-2005)
dimensionless
Elevation Contours from 1500m to 2000m by 500Methodology from Feng, Porporato and Rodriguez-Iturbe, 2013
Additional precipitation occurs in the
winter, which is the wettest part of
the year.

25. Evaporation Changes: 2021-2050 minus 1976-2005
Higher irrigation demands and
evaporative losses from reservoirs.
mm/yr

26. Projected Runoff Changes: 2021-2050 minus 1976-2005
-25 -15 -5 5 15 25
Elevation Contours from 1500m to 2000m by 500
f
Runoff (mm/yr)
-150 -90 -30 30 90 150
c
Basin
Ensemble
Average
Ensemble
Range
Colorado River +9% -3 to 50%
Owens Valley – Mono Lake +9% -13 to 35%
Sacramento River +2% -30 to 22%
San Joaquin – Tulare Lake -1% -27 to 30%
-1 to 9% change ensemble average at basin
level, but with a large range of uncertainty.
mm/yr

27. Runoff Timing Changes (2021-2050 minus 1976-2005)
-8 -4 0 4 8
a
Center of Mass Day (days)
Changes (2021-2050 minus 1976-2005)
Mid-Flow Date (days)
More precipitation falls as Rainfall and snow melts earlier.
• Less natural storage à Artificial storage and flood Issues
Streamflow arrives up to 10 days earlier.
Winter water levels in many reservoirs are kept low for flood control purposes.
• In conflict with storage needs!
Mann-Kendall Trend Test
(Red bars = significant at 5%)

28. Projected Changes (2021-2050 w.r.t. 1976-2005) in 50 year Return Period
c
Annual Cumulative Min Runoff
a
return
period
Projected Changes (2021-2050 w.r.t. 1976-2005) in 50 year Return Volume
Annual Cumulative Min RunoffAnnual Cumulative Max Runoff
0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100
Annual Cumulative Min RunoffAnnual Cumulative Max Runoff
Projected Changes (2021-2050 w.r.t. 1976-2005) in 50 year Return Period
c
Annual Cumulative Min Runoff
a
return
period
Projected Changes (2021-2050 w.r.t. 1976-2005) in 50 year Return Volume
Annual Cumulative Min RunoffAnnual Cumulative Max Runoff
0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100
Annual Cumulative Min RunoffAnnual Cumulative Max Runoff
50-year Cumulative Annual Runoff Changes: 2021-2050 minus 1976-2005
Basin Wet Periods
Colorado River +20% (14 yr)
Owens Valley – Mono Lake +10% (26 yr)
Sacramento River +3% (42 yr)
San Joaquin – Tulare Lake +6% (38 yr)
Increase in both abnormally wet
and dry years (except OV-ML)
• Less normal years
• Less reliability
Projected Changes (2021-2050 w.r.t. 1976-2005) in 50 year Return Period
c
Annual Cumulative Min Runoff
a
return
period
Projected Changes (2021-2050 w.r.t. 1976-2005) in 50 year Return Volume
d
Annual Cumulative Min Runoff
b
Annual Cumulative Max Runoff
0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100
Annual Cumulative Min RunoffAnnual Cumulative Max Runoff
Projected Changes (2021-2050 w.r.t. 1976-2005) in 50 year Return Period
c
Annual Cumulative Min Runoff
a
return
period
Projected Changes (2021-2050 w.r.t. 1976-2005) in 50 year Return Volume
d
Annual Cumulative Min Runoff
b
Annual Cumulative Max Runoff
0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100
Annual Cumulative Min RunoffAnnual Cumulative Max Runoff
Dry Periods
+3% (38 yr)
-4% (69 yr)
+13% (29 yr)
+10% (36 yr) GEV Distribution; Hatchings for KS GOF test at 5%

29. 50-year Runoff Return Period Changes: 2021-2050 minus 1976-2005
Winter reservoir water levels may need to be further lowered for additional
flood control.
In urban locations, flood control channel capacities may need to be increased.
m3/sReturn
Period
2 to 10 times more frequent.
GEV Distribution; Hatchings for KS GOF test at 5%

30. Atmospheric River Frequency
Atmospheric River Intensity
A larger fraction of precipitation falls as
heavy precipitation.
Atmospheric Rivers Changes: 2021-2050 minus 1976-2005
Increase in the frequency of atmospheric
river events, but the average event
magnitude remains similar.

31. Our Future Water Cycle
Present
Future
Substantial reductions in
snowfall (and snowpack).
Increase in “rain flood” risk
Substantial increase in extreme
storm frequency and intensity
Higher irrigation demands and
higher population
Increased summer water deficit
and decreased spring surplus
Precipitation Demand
Runoff
Additional
Deficit
Reduced
SurplusHigher evaporative losses from
reservoirs
Earlier snowmelt
Not all of California’s current
infrastructure is equipped to handle
the increased future winter storage
and flood control requirements.

32. !!!Runoff!&!
Precip.!Extremes!
!!!Droughts!
!!!Temperatures!
!!!Flood!Risk! "!!Snowfall!
Reservoirs!Filled!
Earlier!
!!!Rainfall!
!!!EvapoA
transpiraBon!
!!!PopulaBon!
Reservoir!Water!
Released!Earlier!
"!!Albedo!
Earlier!Snowmelt!
Lack!of!Local!
Supply!Expansion!
!!!IrrigaBon!
Water!Demand!
!!!Indoor!Water!
Demand!
"!!Water!
Security!

33. Population
Populations are projected to rise by
~25% in Southern California by 2050.
http://www.newgeography.com/content/004926-california-2060
Under current climate, if no further
conservation efforts and per capita
use remains the same, 2050 demand
would increase to ~6 km3/yr
Baseline demand: 4.7 km3/yr, 680
liters/capita/day (Italy ~240)

34. Outdoor Irrigation
Turf rebate programs are effective.
Rain barrels, but rains occur when
irriagtion requirements are lowest.
In current Southern Californian climate,
grass lawns require ~1.3 m/yr of water.
• Increasing temperature will likely
increase this demand.
• This may be offset slightly by
increasing precipitation, but
problem of timing (rains in winter).
Urban and agricultural irrigation demands are expected to
increase with climate change and rising population.
Widescale efficient irrigation is needed.

35. Stormwater Capture
Construct infrastructure to store water
off-stream and/or in groundwater banks.
Local annual precipitation is projected to
increase by 3.6 cm but also more
extreme years.
Due to urban development, few suitable
sites exist for stormwater capture.

36. Groundwater Storage
Increase groundwater banking of imported
water, recycled water, and stormwater
• Current imported recharge at 0.9 km3/yr
Depleted aquifers can store water during
abundant years.
• Good alternative to raising reservoirs.

37. Recycled Water
Currently, there is no direct potable reuse
due to negative public perception.
• Not valued as much as potable.
• Used mostly for non-essential uses
(landscape irrigation, cooling towers)
Needs to be a bigger part of the solution.
Currently recycled water generates ~0.4
km3/yr.
Potentially doubling by 2035.

38. Infrastructure
Existing Infrastructure:
• Raise in-stream storage structures.
• Reduce conveyance channel and
pipe leakage and cover aqueducts.
New Infrastructure:
• Stormwater Capture
• Delta 2 Tunnels – Perhaps
https://ww2.kqed.org/science/2016/07/25/about-that-
17-billion-water-project-delta-tunnels-101/

39. Management
http://cw3e.ucsd.edu/FIRO/ - December 2013 Lake Mendocino Example
Agriculture to urban water
transfers.
Reservoir Rule Curve
Reservoir
Storage
Cumulative
Rainfall
Forecast Informed Reservoir
Operations (FIRO).
• Reservoirs water levels are
often lowered in the winter
for flood control purposes.
• Weather forecasts are little
used for reservoir
management.

40. Does Near Term Climate Change Risk Represent
a ‘Yard Sale' for the US Ski Industry?
Daniel Scott1, Brianna R. Pagán2,3,
Robert Steiger4, Moetasim Ashfaq5,
Deeksha Rastogi5, Jeremy S. Pal2 Lake Louise, Canada
321 4 5