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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2017-178
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
19 Apr 2017
Review status
This discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Comparative analyses of hydrological responses of two adjacent watersheds to climate variability and change scenarios using SWAT model
Sangchul Lee1,3, In-Young Yeo1,2, Ali M. Sadeghi3, Gregory W. McCarty3, Wells D. Hively4, Megan W. Lang5, and Amir Sharifi3,6 1Department of Geographical Sciences, University of Maryland, College Park, MD 20742
2School of Engineering, the University of Newcastle, Callaghan NSW 2308, Australia
3USDA-ARS, Hydrology and Remote Sensing Laboratory, Beltsville, MD 20705
4USGS, Eastern Geographic Science Center, Reston, VA 20192
5U.S. Fish & Wildlife Service, National Wetland Inventory, Falls Church, VA 22041
6Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742
Abstract. Water quality problems in the Chesapeake Bay Watershed (CBW) are expected to exacerbate under climate variability and change. However, climate impacts on agricultural lands and resultant nutrient loads into surface water resources are largely unknown. This study evaluates the impacts of climate variability and change on two adjacent watersheds in the Coastal Plain of the CBW, using Soil and Water Assessment Tool (SWAT) model. We prepared six climate sensitive scenarios to assess the individual effects of variations in CO2 concentration (590 and 850 ppm), precipitation increase (11 and 21 %) and temperature increase (2.9 and 5.0 °C), and considered the predicted climate change scenario using five general circulation models (GCMs) under the Special Report on Emissions Scenarios (SRES) A2 scenario. Using SWAT model simulations from 2001 to 2014, as a baseline scenario, the predicted water and nitrate budgets under climate variability and change scenarios were analyzed at multiple temporal scales. Compared to the baseline scenario, precipitation increase of 21 % and elevated CO2 concentration of 850 ppm significantly increased stream flow and nitrate loads by 50 % and 52 %, respectively, while, temperature increase of 5.0 °C reduced stream flow and nitrate loads by 12 % and 13 %, respectively. Under the climate change scenario, annual stream flow and nitrate loads showed an average increase of nearly 40 %, relative to the baseline scenario. Differences in hydrological responses observed from the two watersheds were primarily attributed to contrasting land use and soil characteristics. The watershed with larger percent croplands indicated increased nitrate yield of 0.52 kg N ha−1 compared to the one with less percent croplands under the climate change scenario, due to increased export of nitrate derived from fertilizer. The watershed dominated by poorly-drained soils showed a lower increase in nitrate yield than one dominated by well-drained soils, due to a high potential of nitrate loss in surface runoff and enhanced denitrification. To mitigate increased nitrate loads potentially caused by climate change, the enhanced implementation of conservation practices would be necessary for this region in the future. These findings assist watershed managers and regulators as they seek to establish effective adaptation strategies to mitigate water quality degradation in this region.

Citation: Lee, S., Yeo, I.-Y., Sadeghi, A. M., McCarty, G. W., Hively, W. D., Lang, M. W., and Sharifi, A.: Comparative analyses of hydrological responses of two adjacent watersheds to climate variability and change scenarios using SWAT model, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2017-178, in review, 2017.
Sangchul Lee et al.
Sangchul Lee et al.
Sangchul Lee et al.

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Short summary
Identifying key local factors vulnerable to climate change is imperative for effectively mitigating climate change impacts. This study compared two areas with different characteristics under climate change to examine local factors that worsen current water quality problems. The findings exhibited that nitrate loads tended to increase under climate change and percent croplands were a decisive factor. Therefore, the enhanced implementation of conservation practice would be necessary in the future.
Identifying key local factors vulnerable to climate change is imperative for effectively...
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