Climate Change and
Water Availability Models
Applying climate change predictions
CRWR
Clark Siler
6 Dec 2007
Incorporation of Climate Change in
Water Availability Modeling
by: Wurbs, RA
Physical Climatology Class Presentation
University of Texas at Austin
Climate Change and Water Availability Models
Freshwater Demand is Increasing
• Increases in Population
• Urbanization
• Increasing Wealth
• Aquifer Depletion
• Pollution
• Climate Change
Climate Change and Water Availability Models
Water Availability in Texas
• Drought of 1996
– Widespread drought where decision-makers
had no information on water availability
• Senate Bill 1, “Water Bill”
– Passed in response to drought
• Water Rights Analysis Package (WRAP)
– Texas’ official water availability model
Climate Change and Water Availability Models
Water Rights Analysis Package
• Origin and Use
– Suite of programs to digitally model and
manage water rights in Texas
– Developed by Dr. Ralph Wurbs of the Texas
Water Resources Institute at Texas A&M
– Created ~20 years ago, but gained increased
use after Senate Bill 1 (1997)
– Official Water Availability Model of Texas
Climate Change and Water Availability Models
WRAP Process
Description
Evaporation Data
Develops naturalized flows and reservoir
evaporation and precipitation rates for
use in WRAP-SIM.
WRAP-HYD
Process
Pre-Process
Historical Flow
FLO
EVA
FLO
EVA
Tracks river flows and reservoir levels
for allocation of water rights.
WRAP-SIM
MSS
OUT
YRO
Results are a message file (MSS), yieldreliability analysis output table (YRO),
and main results output file (OUT).
Used for organizing, summarizing,
analyzing, and displaying simulation
results.
OUT
Post-Process
WRAP-SIM
TABLES
WinWRAP
WRAP-HYD
Structure
TABLES
OUT
Excel
Includes options for further calculations,
such as statistical analyses.
Climate Change and Water Availability Models
Naturalized Flows?
Climate Change and Water Availability Models
Naturalized Flows
• WRAP is Based on Naturalized Flows
NF = GF + SDi – SRFi + SEPi + SDSi
NF
GF
D
RF
EP
DS
naturalized flow
gaged flow
water supply diversions upstream
return flow upstream
reservoir evaporation minus precipitation
change in storage in upstream reservoirs
EP
DS
D
RF
GF
• Used to predict reliabilities (water availability)
NF
Climate Change and Water Availability Models
WRAP and Climate Change
• WRAP cannot directly model climate
change
• WRAP inputs can be modified to reflect
climate change modeled predictions
Climate Change and Water Availability Models
Modeling Climate Change
Essentially, all models are wrong, but some are useful.
George Box, industrial statistician
• Models Used in Main Paper:
– Soil and Water Assessment Tool (SWAT)
– Canadian Centre for Climate Modelling and
Analysis GCM (CCCma)
Climate Change and Water Availability Models
Soil and Water Assessment
Tool (SWAT)
• Inputs:
–
–
–
–
–
–
–
–
Precipitation
Max/Min Temperature
Land Use
Soils
Land Management
Topography
Hydrogeology
Weather
http://www.brc.tamus.edu/swat/
SWAT is a watershed modeling tool
• Output:
– Daily Streamflow
• Hydrologic Unit Model of the United States (HUMUS):
– Relative Humidity
– Solar Radiation
– Wind Speed
Climate Change and Water Availability Models
Canadian Centre for Climate
Modelling and Analysis GCM
(CCCma)
http://www.cccma.bc.ec.gc.ca/
• Coupled Atmosphere-Ocean Dynamics Model
– Inputs include:
•
•
•
•
specific humidity
precipitation
soil moisture
cloud cover
•
•
•
•
moist convection
radiative heating
CO2 concentration
sea level pressure
•
•
•
•
global mean surface temperature
ocean circulation
sea ice / snow
seasonally frozen soil moisture
– Output includes precipitation and max/min temperature
– Includes climate-change scenario, IS92a, which employs CO2
increase of 1% per year
– Not a toy model
– CCCma predictions are relatively high compared to other models
• Aggressive climate change model
• Is this preferable in this case?
Climate Change and Water Availability Models
Combining Models
• Uncertainty may be introduced when
combining a global and basin-scale model
Climate Change and Water Availability Models
Climate Change and WRAP
1.
2.
3.
4.
Precipitation and temperature modeled results
for 2040-2060 are retrieved from the CCCma
GCM results: one set reflecting climate change,
one without climate change.
GCM modeled data is used to alter SWAT input
which is used as a representation of 2050
climate.
SWAT uses this data along with historical data
to produce sets of daily streamflow values.
These are used to adjust WRAP inputs of
naturalized flows (and reservoir evaporation).
WRAP is run with historical and climate
changed data. Results are used to assess
possible future water availability.
CCCma
Output
Input
Output
Input
Output
Climate Change and Water Availability Models
Conclusion
• Climate change analyses introduce additional
uncertainties to the highly stochastic water
resources environment
• WRAP can be used to model future climate
changed water availability
– Can analyze various climate change scenarios
• Similar processes can be executed to use any
combination of compatible climate models
Physical Climatology Class Presentation
University of Texas at Austin
Personal Information
• Clark Siler
Graduate Student
University of Texas at Austin
Geospatial Hydrology
Water Resources
CRWR
BS – Brigham Young University
Civil Engineering
clarksiler@mail.utexas.edu
Nov 2007