| Title: | Assessing the impacts of future climate conditions on the effectiveness of winter cover crops in reducing nitrate loads into the Chesapeake Bay watersheds using the SWAT Model |
| Authors: | Lee, S., A.M. Sadeghi, I.-Y. Yeo, G.W. McCarty and W.D. Hively |
| Year: | 2017 |
| Journal: | Transactions of the ASABE |
| Volume (Issue): | 60(6) |
| Pages: | 1939-1955 |
| Article ID: | |
| DOI: | 10.13031/trans.12390 |
| URL (non-DOI journals): | |
| Model: | SWAT |
| Broad Application Category: | hydrologic and pollutant |
| Primary Application Category: | BMP and/or cropping system assessment |
| Secondary Application Category: | climate change |
| Watershed Description: | 220.7 km^2 Tuckahoe Creek and 290.1 km^2 Greensboro River, tributaries of the Choptank River that drain portions of west central Delaware and/or eastern Maryland and are located on the Delmarva Peninsula, U.S. |
| Calibration Summary: | |
| Validation Summary: | |
| General Comments: | |
| Abstract: | Winter cover crops (WCCs) have been widely implemented in the Coastal Plain of the Chesapeake Bay watershed (CBW) due
to their high effectiveness at reducing nitrate loads. However, future climate conditions (FCCs) are expected to exacerbate
water quality degradation in the CBW by increasing nitrate loads from agriculture. Accordingly, the question remains whether
WCCs are sufficient to mitigate increased nutrient loads caused by FCCs. In this study, we assessed the impacts of FCCs on
WCC nitrate reduction efficiency on the Coastal Plain of the CBW using Soil and Water Assessment Tool (SWAT) model. Three
FCC scenarios (2085 – 2098) were prepared using General Circulation Models (GCMs), considering three Intergovernmnental
Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) greenhouse gas emission scenarios. We also
developed six representative WCC implementation scenarios based on the most commonly used planting dates and species of
WCCs in this region. Simulation results showed that WCC biomass increased by ~ 58 % under FCC scenarios, due to climate
conditions conducive to the WCC growth. Prior to implementing WCCs, annual nitrate loads increased by ~ 43 % under FCC
scenarios compared to the baseline scenario (2001 – 2014). When WCCs were planted, annual nitrate loads were substantially
reduced by ~ 48 % and WCC nitrate reduction efficiency water ~ 5 % higher under FCC scenarios relative to the baseline
condition. The increase rate of WCC nitrate reduction efficiency varied by FCC scenarios and WCC planting methods. As
CO2 concentration was higher and winters were warmer under FCC scenarios, WCCs had greater biomass and therefore
2
showed higher nitrate reduction efficiency. In response to FCC scenarios, the performance of less effective WCC practices
(e.g., barley, wheat, and late planting) under the baseline indicated ~ 14 % higher increase rate of nitrate reduction efficiency
compared to ones with better effectiveness under the baseline (e.g., rye and early planting), due to warmer temperatures.
According to simulation results, WCCs were effective to mitigate nitrate loads accelerated by FCCs and therefore the role of
WCCs in mitigating nitrate loads is even more important in the given FCCs. |
| Language: | English |
| Keywords: | Winter cover crops (WCCs), Future climate conditions (FCCs), Water quality, SWAT. |