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Climate Change Effects on Flow and Water Quality in Upper Mississippi River Basin

This study explores the potential impacts of climate change on flow and water quality in the Upper Mississippi River Basin using a hydrological model. The research includes calibration and validation of the model, as well as analyzing various climate inputs and their effects on stream flow. The study also discusses the potential changes in water quality due to climate change. More research is needed to fully understand the impact on water quality.

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Climate Change Effects on Flow and Water Quality in Upper Mississippi River Basin

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  1. Image courtesy of NASA/GSFC

  2. Potential Climate Change Impacts on Flow and Water Quality in the Upper Mississippi River Basin Eugene S. Takle Iowa State University Ames, IA 50011 USA gstakle@iastate.edu Project collaborators: Manoj Jha, Zaitao Pan, Roy Gu Iowa-Minnesota Drainage Research Forum 27 November 2007

  3. Outline • Domain and hydrological model (SWAT) • Calibration and validation • Observations -> stream flow • NNR -> RCM -> SWAT-> stream flow • GCM -> RCM -> SWAT-> stream flow • GHG -> GCM -> RCM -> SWAT -> stream flow • Stream flow vs. precipitation For details see: Jha, M., Z. Pan, E. S. Takle, and R. Gu, 2003: Impacts of climate change on stream flow in the Upper Mississippi River Basin: A regional climate model perspective. Journal of Geophysical Research.

  4. Sub-Basins of the Upper Mississippi River Basin 119 sub-basins Outflow measured at Grafton, IL Approximately one observing station per sub-basin Approximately one model grid point per sub-basin

  5. Soil Water Assessment Tool (SWAT) • Long-term, continuous watershed simulation model (Arnold et al,1998) • Daily time steps • Assesses impacts of climate and management on yields of water, sediment, and agricultural chemicals • Physically based, including hydrology, soil temperature, plant growth, nutrients, pesticides and land management

  6. SWAT Output with Various Sources of Climate Input

  7. Calibration of SWAT: Annual Stream Flow at Grafton, IL

  8. Calibration of SWAT: Monthly Stream Flow at Grafton, IL

  9. Validation of SWAT: Annual Stream Flow at Grafton, IL

  10. Validation of SWAT: Monthly Stream Flow at Grafton, IL

  11. RegCM2 Simulation Domain Red = global model grid point Green/blue = regional model grid points

  12. Annual Stream Flow Simulated by SWAT Driven by the RegCM2 Regional Climate Model with NNR Lateral Boundary Conditions

  13. Mean Monthly Precipitation Simulated by the RegCM2 Regional Climate Model with NNR Lateral Boundary Conditions

  14. Seasonal Stream Flow Simulated by SWAT Driven by the RegCM2 Regional Climate Model with NNR Lateral Boundary Conditions

  15. Hydrological component comparison • between RegCM2 and SWAT Note: All values are in mm per year averaged for 1980-1988 in NNR run.

  16. SWAT Output with Various Sources of Climate Input

  17. Ten-Year Mean Monthly Stream Flow Generated by the RegCM2 Regional Climate Model Driven with HadCM2 Global Model Results for the Contemporary and Future Scenario (2040s) Climate

  18. Ten-Year Mean Precipitation Generated by the RegCM2 Regional Climate Model Driven with HadCM2 Global Model Results for the Contemporary and Future Scenario (2040s) Climate

  19. Errors in Simulated Stream Flow and Climate Change

  20. Comparison of Simulated Stream Flow under Climate Change with Various Model Biases

  21. Hydrologic Budget Components Simulated by SWAT under Different Climates All units are mm Yield is sum of surface runoff, lateral flow, and groundwater flow

  22. Relation of Runoff to Precipitation for Various Climates

  23. Regression Analysis: Stream Flow vs. Precipitation

  24. Water Quality(Results from GCM Study) • Fugitive nitrates and sediment from the landscape are both carried by overland flow related to runoff • The dominant pathway for nitrate loss is through leaching to groundwater and then via baseflow or tile drains (Randall, 2001). • Results show a substantial decrease in runoff in the future climate but increase in baseflow, although with less agreement among models.

  25. Water Quality(Results from GCM Study) • Both sediment and nitrate loading of streams would decrease due to decreased runoff but nitrate leaching might increase. • Although water quality might improve due to reduced sediment, the loading due to nitrates is less clear but might increase.

  26. Summary • RCM provides meteorological detail needed by SWAT to resolve sub-basin variability of importance to streamflow • There is strong suggestion that climate change introduces changes of magnitudes larger than variation introduced by the modeling process • Relationship of streamflow to precipitation might change in future scenario climates • More research is needed to assess impact on water quality

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