SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Effect of irrigation and climate variability on water quality of coastal watersheds: Case study in Alabama 
Authors:Mirhosseini, G. and P. Srivastava 
Journal:Journal of Irrigation and Drainage Engineering 
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URL (non-DOI journals): 
Broad Application Category:hydrologic & pollutant 
Primary Application Category:irrigation impacts or irrigation BMP scenarios 
Secondary Application Category:ENSO phenomena effects 
Watershed Description:80.24 km^2 Big Creek, located in Mobile County in southwest Alabama,U.S. 
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Validation Summary: 
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Abstract:Agricultural activities are considered the leading cause of surface water quality degradation in the United States. While agricultural production in the state of Alabama is mainly rain-fed, irrigation is currently being promoted to reduce drought vulnerability associated with the El Niño Southern Oscillation (ENSO). It is not clear, however, how increased irrigation and ENSO-induced seasonal to interannual climate variability will affect the transport of pollutants [mainly nitrogen (N) and phosphorus (P)] to surface water bodies. The objective of this study was to quantify the effect of irrigation and ENSO on nutrient transport. A standard model to assess soil and water was applied in the Big Creek watershed of southwest Alabama to address this objective. The hydrologic and water quality parameters of the model were calibrated and validated by comparing model predictions with 15 years of observed data, and the effect of irrigation was evaluated. Model simulations were performed for 59 years (1950–2008) to quantify the effect of ENSO on nutrient transport. Results show that total nitrogen (TN) and total phosphorus (TP) loads increased by 4 and 3%, respectively, when irrigation was applied to cropland subwatersheds. The increase in TN load was significant at 90% confidence level (α ¼ 0.10), while the increase in the TP load was nonsignificant at α ¼ 0.1, indicating that TN= transport is more sensitive to irrigation. Further, results suggest that El Niño generates higher nutrient loads in November, January, February, May, and July as compared to La Niña. Overall, irrigation increased nutrient transport (especially TN) within the watershed; this increase was affected by ENSO, with the El Niño phase generating greater loads than the La Niña and Neutral phases. However, inappropriate management of nutrient application can lead to greater negative impacts on water quality than irrigation. Although, the study only examined one coastal plain watershed, the results are expected to be applicable to much of the ENSO-affected coastal plain area of the southeast United States. 
Keywords:Irrigation; Water quality; El Niño southern oscillation (ENSO); Modeling; Soil and water assessment tool (SWAT).