Hu X, McIsaac G F, David M B, Louwers C A L
Department of Civil and Environmental Engineering, Urbana, IL, USA.
J Environ Qual. 2007 May 25;36(4):996-1005. doi: 10.2134/jeq2006.0228. Print 2007 Jul-Aug.
Reliable water quality models are needed to forecast the water quality consequences of different agricultural nutrient management scenarios. In this study, the Soil and Water Assessment Tool (SWAT), version 2000, was applied to simulate streamflow, riverine nitrate (NO(3)) export, crop yield, and watershed nitrogen (N) budgets in the upper Embarras River (UER) watershed in east-central Illinois, which has extensive maize-soybean cultivation, large N fertilizer input, and extensive tile drainage. During the calibration (1994-2002) and validation (1985-1993) periods, SWAT simulated monthly and annual stream flows with Nash-Sutcliffe coefficients (E) ranging from 0.67 to 0.94 and R(2) from 0.75 to 0.95. For monthly and annual NO(3) loads, E ranged from -0.16 to 0.45 and R(2) from 0.36 to 0.74. Annual maize and soybean yields were simulated with relative errors ranging from -10 to 6%. The model was then used to predict the changes in NO(3) output with N fertilizer application rates 10 to 50% lower than original application rates in UER. The calibrated SWAT predicted a 10 to 43% decrease in NO(3) export from UER and a 6 to 38% reduction in maize yield in response to the reduction in N fertilizer. The SWAT model markedly overestimated NO(3) export during major wet periods. Moreover, SWAT estimated soybean N fixation rates considerably greater than literature values, and some simulated changes in the N cycle in response to fertilizer reduction seemed to be unrealistic. Improving these aspects of SWAT could lead to more reliable predictions in the water quality outcomes of nutrient management practices in tile-drained watersheds.
需要可靠的水质模型来预测不同农业养分管理情景下的水质后果。在本研究中，应用2000版土壤和水资源评估工具（SWAT）来模拟伊利诺伊州中东部恩巴拉斯河上游（UER）流域的径流、河流硝酸盐（NO₃）输出、作物产量和流域氮（N）预算，该流域有广泛的玉米 - 大豆种植、大量氮肥投入和广泛的瓦管排水。在校准期（1994 - 2002年）和验证期（1985 - 1993年），SWAT模拟的月径流和年径流的纳什 - 萨特克利夫系数（E）范围为0.67至0.94，决定系数（R²）范围为0.75至0.95。对于月和年NO₃负荷，E范围为 - 0.16至0.45，R²范围为0.36至0.74。模拟的年度玉米和大豆产量的相对误差范围为 - 10%至6%。然后该模型用于预测UER流域氮肥施用量比原施用量低10%至50%时NO₃输出的变化。校准后的SWAT预测，由于氮肥减少，UER流域的NO₃输出将减少10%至43%，玉米产量将减少6%至38%。SWAT模型在主要湿润期显著高估了NO₃输出。此外，SWAT估计的大豆固氮率远高于文献值，并且一些因肥料减少而模拟的氮循环变化似乎不切实际。改进SWAT的这些方面可能会使瓦管排水流域养分管理实践的水质结果预测更加可靠。
