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Global pattern of trends in streamflow and water availability in a changing climate

Global pattern of trends in streamflow and water availability in a changing climate. By Milly, PCD, DA Dunne, and AV Vecchia In: Nature vol. 438 (17), pp. 347-351 (2005). General Question. How will climate change impact the water cycle on regional and global scales? -streamflow

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Global pattern of trends in streamflow and water availability in a changing climate

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  1. Global pattern of trends in streamflow and water availability in a changing climate By Milly, PCD, DA Dunne, and AV Vecchia In: Nature vol. 438 (17), pp. 347-351 (2005)

  2. General Question How will climate change impact the water cycle on regional and global scales? -streamflow -precipitation -temperature

  3. Climate and Hydrology • Temperature, SVP • Precipitation shifts, regional • Streamflow=P-ET • when averaged over many years • for large river basins

  4. Methods, briefly • Streamflow volume • 165 large rivers, globally distributed • 28-99 years of streamflow data collection • Climate models • To predict streamflow from precipitation and temperature changes • 14 models aggregated • Approach: • Compare modeled streamflow to known streamflow • Predict future streamflow with most accurate models

  5. Regions of Predicted Streamflow Increase by 10-40%, during 2041-2060 La Plata Basin Eastern equatorial Africa http://upload.wikimedia.org www.coffeeproject.com www.gewex.org/LPB.htm high latitude North America and Eurasia

  6. Regions of Predicted Streamflow Decrease • by 10-30%, during 2041-2060 upload.wikimedia.org http://www.greatdreams.com/soeurope.jpg Southern Europe Southwest North America Middle East Southern Africa http://www.travelblog.org/pix/maps/middle-east.jpg http://www.acipco.com

  7. The Skeptics Say… • Runoff equates with “sustainable water availability”??? • Pollution • Groundwater • Irrigation • Questionable model accuracy • Large variability in each model’s predicted streamflow • Does aggregating the 14 most-accurate models solve the problem? • 28 vs. 99 years of data • Low correlation between observations and model output: .34 • Streamflow prediction assumptions: • Future greenhouse gas emissions • Volcanic activity • Solar activity • Temporal lag in streamflow, due to storage

  8. What’s Missing? • Further data collection? • Resource management implications? • Are the results valid, useful?

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