Climate Change and Water Availability Models Applying climate change predictions Clark Siler 6 Dec 2007 Physical Climatology Class Presentation University of Texas at Austin Incorporation of Climate Change in Water Availability Modeling by: Wurbs, RA

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

Naturalized Flows ? Climate Change and Water Availability Models

Naturalized Flows WRAP is Based on Naturalized Flows NF naturalized flow GF gaged flow D water supply diversions upstream RFreturn flow upstream EPreservoir evaporation minus precipitation  Schange in storage in upstream reservoirs Used to predict reliabilities (water availability) NF = GF +  D i –  RF i +  EP i +   S i NF GF D RF EP SS

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 Models Used in Main Paper: –Soil and Water Assessment Tool (SWAT) –Canadian Centre for Climate Modelling and Analysis GCM (CCCma) Essentially, all models are wrong, but some are useful. George Box, industrial statistician

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 Hydrologic Unit Model of the United States (HUMUS): –Relative Humidity –Solar Radiation –Wind Speed Output: –Daily Streamflow SWAT is a watershed modeling tool

Climate Change and Water Availability Models Canadian Centre for Climate Modelling and Analysis GCM (CCCma) Coupled Atmosphere-Ocean Dynamics Model –Inputs include: –Output includes precipitation and max/min temperature –Includes climate-change scenario, IS92a, which employs CO 2 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? specific humidity precipitation soil moisture cloud cover moist convection radiative heating CO 2 concentration sea level pressure global mean surface temperature ocean circulation sea ice / snow seasonally frozen soil moisture

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.Precipitation and temperature modeled results for are retrieved from the CCCma GCM results: one set reflecting climate change, one without climate change. 2.GCM modeled data is used to alter SWAT input which is used as a representation of 2050 climate. 3.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). 4.WRAP is run with historical and climate changed data. Results are used to assess possible future water availability. Output Input

Climate Change and Water Availability Models Physical Climatology Class Presentation University of Texas at Austin Physical Climatology Class Presentation University of Texas at Austin 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

Personal Information Clark Siler Graduate Student University of Texas at Austin Geospatial Hydrology Water Resources CRWR BS – Brigham Young University Civil Engineering CRWR Nov 2007