A combined water balance and tree ring approach to understanding the potential hydrologic effects of climate change in the central Rocky Mountain region

作者：Gray Stephen T^*; McCabe Gregory J

来源：Water Resources Research, 2010, 46: W05513.

DOI：10.1029/2008WR007650

Models suggest that average temperatures in the central Rocky Mountains will increase by >3 degrees C over the next century, while precipitation may remain within late Holocene boundaries. This study investigates the potential hydrologic effects of such warming when combined with the full range of precipitation variability experienced over the past millennium. Using the upper Yellowstone drainage as a test case, a water balance model is constructed to estimate river discharge from precipitation and temperature inputs (r = 0.85 versus observed). The model then was run using tree ring precipitation estimates for 1177-1910 and 1911-1995 A. D. combined with (1) average observed temperatures 1896-1995; (2) reconstructed Northern Hemisphere temperatures since 1177; or (3) Intergovernmental Panel on Climate Change temperature projections for 2025, 2050, and 2100. Discharge estimates generated by driving the model with tree ring precipitation for 1911-1995 and observed temperatures served as a baseline for comparisons with other climate runoff scenarios. All combinations of the various temperature scenarios and pre-1911 precipitation resulted in mean discharge below the gauge period baseline. Projected temperatures for 2050 and 2100 produced the lowest mean discharge at 85% and 76% of baseline, respectively. Combining observed temperatures with the paleoprecipitation scenarios created numerous multidecadal periods with discharge <85% of baseline. Discharge during these same multidecadal droughts declined an additional 16-34% under the 2025-2100 temperature regimes. Likewise inherent multidecadal precipitation variability adds a large degree of nonstationarity to the climate change responses seen in discharge estimates. While this combined tree ring and water balance scenario exercise does not provide precise forecasts for future conditions, these results suggest that a 1 degrees-3 degrees C warming could have major negative effects on water availability in the upper Yellowstone. These results also indicate that twentieth-century observations paint an incomplete and potentially overly optimistic picture of regional water supplies.

• 出版日期2010-5-6