Grantee Research Project Results
2013 Progress Report: Modeling of the Hydrochemical Response of High Elevation Watersheds to Climate Change and Atmospheric Deposition
EPA Grant Number: R834188Title: Modeling of the Hydrochemical Response of High Elevation Watersheds to Climate Change and Atmospheric Deposition
Investigators: Driscoll, Charles T. , Campbell, John L. , Hayhoe, Katharine , Wu, Wei
Current Investigators: Driscoll, Charles T. , Campbell, John L. , Pourmokhtarian, Afshin , Hayhoe, Katharine , Wu, Wei , Dong, Zheng
Institution: Syracuse University , University of Southern Mississippi , USDA , Towson University
Current Institution: Syracuse University , Towson University , USDA , University of Southern Mississippi
EPA Project Officer: Packard, Benjamin H
Project Period: August 1, 2009 through July 31, 2012 (Extended to July 31, 2014)
Project Period Covered by this Report: August 1, 2012 through July 31,2013
Project Amount: $800,000
RFA: Consequences of Global Change for Water Quality (2008) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration , Watersheds , Water , Climate Change
Objective:
The impacts of changing climate on terrestrial ecosystems have been assessed by observational, gradient, laboratory and field studies. However, state-of-the-art biogeochemical models provide an important tool to investigate climatic perturbations to complex ecosystems.
The overarching goal for this study is to compare model calculations across high elevation watersheds in the United States with a range of climatic conditions to better understand and quantify how the quantity and quality of surface waters might respond to changing climate.
To achieve this goal, we are using the hydrochemical model, PnET-BGC, driven by both past and future simulated climate, to assess the impact of climate change on watershed processes and water quantity and quality. Climate input scenarios are generated with well-documented statistical downscaling procedures based on simulations from outputs from the latest atmosphere ocean global circulation models (AOGCMs) available from the Intergovernmental Panel on Climate Change (IPCC). Using these climate input data, PnET-BGC is being run at the 14 high elevation watersheds in the United States. This approach enables us to evaluate hydrochemical responses intensively at local scales and more broadly at regional and national scales. We are working with cooperating scientists from the intensive study sites to interpret model results and design additional analyses.
Progress Summary:
The fully integrated coupled hydrological and biogeochemical model (PnET-BGC) was applied to evaluate the effects of climate change and increasing concentrations of atmospheric carbon dioxide at seven diverse, intensively studied, high-elevation watersheds and to evaluate aspects of these applications. Coarse scale projections from global circulation models were downscaled to local watersheds and applied as inputs to the biogeochemical model, PnET-BGC.
PnET-BGC was used to evaluate the direct and indirect effects of global change drivers (i.e., temperature, precipitation, solar radiation, carbon dioxide) on biogeochemical processes in a northern hardwood forest ecosystem at the Hubbard Brook Experimental Forest, NH. A sensitivity analysis was conducted to better understand how the model responds to variation in climatic drivers, showing that forest watershed ecosystem processes are sensitive to temperature, precipitation and photosynthetically active radiation inputs. Model calculations suggested that future changes in climate that induce water stress (decreases in summer soil moisture due to shifts in hydrology and increases in evapotranspiration), uncouple plant-soil linkages allowing for increases in net mineralization of soil nitrogen and nitrification and elevated leaching losses of nitrate that result in soil and water acidification. Anticipated forest fertilization associated with increases in atmospheric carbon dioxide appears to mitigate this perturbation somewhat. This work was published in Pourmokhtarian et al. (2012).
Two different statistical downscaling approaches- Bias Correction-Spatial Disaggregation (Grid-based) and Asynchronous Regional Regression Model (station-based) – were compared on potential hydrochemical projections of future climate at the Hubbard Brook Experimental Forest, NH. The choice of downscaling approach has important implications for streamflow simulations, which is directly related to the ability of the downscaling approach to mimic observed precipitation patterns. The climate and streamflow change signals indicate that the current hydrologic discharge regime with snowmelt-driven spring-flows in April will likely shift to conditions dominated by larger flows throughout winter. Model results from grid-based downscaling show that warmer future temperatures cause midsummer drought stress, which uncouples plant-soil linkages, leading to an increase in net soil nitrogen mineralization and nitrification, and acidification of soil and streamwater. In contrast, the precipitation inputs depicted by station-based downscaling are adequate to overcome the risk of drought stress due to greater estimates of precipitation inputs. This component of the research indicates that station-based downscaling should be used in climate projections in complex mountainous terrain.
A cross-site analysis of seven intensive study sites in the northeastern United States with diverse characteristics of climate, soil and vegetation type, and historical land disturbances was conducted to assess the range of forest-watershed responses to changing climate. The watersheds studied included the Hubbard Brook Experimental Forest, NH; the Fernow Experimental Forest, WV; Sleepers River Watershed, VT; the Huntington Wildlife Forest, NY; Biscuit Brook Watershed, NY; Cone Pond Watershed, NH; and Bear Brook Watershed, ME. Model results show that evapotranspiration increases across all watersheds under potential future conditions of warmer temperature and longer growing season. Climate projections suggest that spruce-fir forests will likely experience temperature stress and decline in productivity, while some of the northern hardwood forests are likely to experience water stress due to early loss of snowpack, longer growing season and associated water deficit. This latter response is somewhat counter-intuitive as most sites are expected to experience increases in precipitation. Following increases in temperature, evapotranspiration and water stress associated with future climate change scenarios, a shifting pattern in carbon allocation in plants was evident causing significant changes in net primary production. The soil organic carbon pool is projected to decrease significantly across all Northeast forest watersheds and showed a strong negative relationship with increases in temperature. Cross-site analysis among different watersheds in the Northeast indicated that dominant type of vegetation, geological characteristics and historical land disturbances coupled with climate variability will influence future hydrochemical responses of watersheds to climate change.
In addition to the Northeast watersheds, model simulations are also being conducted for Coweeta Hydrologic Laboratory, NC; Saunders River, VA; White Oak Run, VA; Niwot Ridge, CO; Andrews Experimental Forest, OR; and the Smoky Mountain National Park, TN, NC.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
| Other project views: | All 26 publications | 7 publications in selected types | All 6 journal articles |
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Brown A. Hydrology: catchment interactions. Nature Climate Change 2012;2:486. |
R834188 (2013) |
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Campbell JL, Driscoll CT, Pourmokhtarian A, Hayhoe K. Streamflow responses to past and projected future changes in climate at the Hubbard Brook Experimental Forest, New Hampshire, United States. Water Resources Research 2011;47(2):W02514 (15 pp.). |
R834188 (2010) R834188 (2011) R834188 (2013) R834188 (Final) |
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Pourmokhtarian A, Driscoll CT, Campbell JL, Hayhoe K. Modeling potential hydrochemical responses to climate change and increasing CO2 at the Hubbard Brook Experimental Forest using a dynamic biogeochemical model (PnET-BGC). Water Resources Research 2012;48(7):W07514 (13 pp.). |
R834188 (2011) R834188 (2012) R834188 (2013) R834188 (Final) |
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Supplemental Keywords:
Air, RFA, climate change, air pollution effects, atmosphere, global climate change, hydrologic models, atmospheric models, watersheds, RFA, Air, Atmosphere, Air Pollution Effects, climate change, Global Climate Change, hydrologic models, environmental monitoringProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.