Abstract
Two comprehensive agricultural watershed-scale hydrological models: Soil and Water Assessment Tool (SWAT), and Annualized Agricultural Non-Point Source Pollution Model (AnnAGNPS), have been widely used for evaluating agricultural Best Management Practice (BMP). In this study, models were developed for the Big Sunflower River Watershed (BSRW) in Mississippi, USA. Both hydrological models were successfully calibrated and validated for predicting monthly stream flow discharges from three USGS gages (Merigold, Sunflower, and Leland) within the BSRW. The model performances were reasonable with R 2 and NSE values range from 0.45 to 0.84 for SWAT, and from 0.34 to 0.66 for AnnAGNPS. Both models predicted lower stream flow discharge with conservation tillage practice as compare to conventional tillage practice BMP evaluated in this study. Overall, results showed that both SWAT and AnnAGNPS models successfully simulated hydrological conditions of the watershed with agricultural BMP, and these models can be useful for making hydrological decisions related to agricultural watershed managements. Keywords: SWAT, AnnAGNPS, tillage, streamflow, hydrology, BMP DOI: 10.7176/JEP/12-3-03 Publication date: January 31 st 2021
Highlights
With greater understanding of watershed hydrology, various modeling tools were developed to simulate watershed hydrological processes
3.1 Calibration and validation The Soil and Water Assessment Tool (SWAT) and AnnAGNPS models calibration results for stream flow showed reasonable performance based on R2 and Nash–Sutcliffe model efficiency coefficient (NSE) values (Moriasi et al, 2015; Table 1)
The AnnAGNPS model considered the retention parameter that is an important parameter in Soil Conservation Service (SCS) curve number method varies with soil moisture content, while SWAT model considered the retention parameter varies with plant potential evapotranspiration in addition to soil moisture content (Bingner et al, 2015; Neitsch et al, 2011)
Summary
With greater understanding of watershed hydrology, various modeling tools were developed to simulate watershed hydrological processes. Hydrologic Modeling System (HEC-HMS - Feldman, 2000) developed by the United States Army Corps of Engineers Hydrologic Engineering Center is a runoff simulating tool with several options including continuous simulation. Agricultural activities such as intensive fertilization and tillage operation could have great influences on surface water quality as well as water quantity (Ayers & Westcot, 1985; Shipitalo & Edwards, 1998; Vaché et al, 2002). The selected simulating tool need to account for both hydrologic and agricultural activities during simulation
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