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Comparative analyses of hydrological responses of two adjacent watersheds to climate variability and change using the SWAT model.

Comparative analyses of hydrological responses of two adjacent watersheds to climate variability and change using the SWAT model.

Authors :
Lee, Sangchul
Yeo, In-Young
Sadeghi, Ali M.
McCarty, Gregory W.
Hively, Wells D.
Lang, Megan W.
Sharifi, Amir
Source :
Hydrology & Earth System Sciences; 2018, Vol. 22 Issue 1, p689-708, 20p, 10 Charts, 8 Graphs, 2 Maps
Publication Year :
2018

Abstract

Water quality problems in the Chesapeake Bay Watershed (CBW) are expected to be exacerbated by climate variability and change. However, climate impacts on agricultural lands and resultant nutrient loads into surface water resources are largely unknown. This study evaluated the impacts of climate variability and change on two adjacent watersheds in the Coastal Plain of the CBW, using the Soil andWater Assessment Tool (SWAT) model.We prepared six climate sensitivity scenarios to assess the individual impacts of variations in CO<subscript>2</subscript> concentration (590 and 850 ppm), precipitation increase (11 and 21 %), and temperature increase (2.9 and 5.0 °C), based on regional general circulation model (GCM) projections. Further, we considered the ensemble of five GCM projections (2085-2098) under the Representative Concentration Pathway (RCP) 8.5 scenario to evaluate simultaneous changes in CO<subscript>2</subscript>, precipitation, and temperature. Using SWAT model simulations from 2001 to 2014 as a baseline scenario, predicted hydrologic outputs (water and nitrate budgets) and crop growth were analyzed. Compared to the baseline scenario, a precipitation increase of 21% and elevated CO<subscript>2</subscript> concentration of 850 ppm significantly increased streamflow and nitrate loads by 50 and 52 %, respectively, while a temperature increase of 5.0 °C reduced streamflow and nitrate loads by 12 and 13 %, respectively. Crop biomass increased with elevated CO<subscript>2</subscript> concentrations due to enhanced radiation- and water-use efficiency, while it decreased with precipitation and temperature increases. Over the GCM ensemble mean, annual streamflow and nitrate loads showed an increase of ~70%relative to the baseline scenario, due to elevated CO<subscript>2</subscript> concentrations and precipitation increase. Different hydrological responses to climate change were observed from the two watersheds, due to contrasting land use and soil characteristics. The watershed with a larger percent of croplands demonstrated a greater increased rate of 5.2 kgNha<superscript>-1</superscript> in nitrate yield relative to the watershed with a lower percent of croplands as a result of increased export of nitrate derived from fertilizer. The watershed dominated by poorly drained soils showed increased nitrate removal due do enhanced denitrification compared to the watershed dominated by well-drained soils. Our findings suggest that increased implementation of conservation practices would be necessary for this region to mitigate increased nitrate loads associated with predicted changes in future climate. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
10275606
Volume :
22
Issue :
1
Database :
Complementary Index
Journal :
Hydrology & Earth System Sciences
Publication Type :
Academic Journal
Accession number :
127781015
Full Text :
https://doi.org/10.5194/hess-22-689-2018