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| Uncertainty analysis of an AnnAGNPS model used in the Chakou watershed |
| Received:September 19, 2017 |
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| KeyWord:AnnAGNPS;parameter sensitivity analysis;uncertainty analysis;Morris classification;FOEA;Bootstrap;Chakou watershed |
| Author Name | Affiliation | E-mail | | LOU Yong-cai | College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China | | | GUO Qing-xia | College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, China | gqx696@163.com |
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| Abstract: |
| In order to reduce the uncertainty of model simulations and improve the applicability of models in the Chakou watershed of a typical loess hilly-gully region, in this study, we selected ten parameters of an AnnAGNPS model and used the Morris classification method to analyze the sensitivity of the parameters to the simulation results of the model. The uncertainty analysis method FOEA(First-order error analysis) and Bootstrap were adopted to identify important uncertain parameters and evaluate the contribution of these parameters to the uncertainty of the model output variables. The following results were obtained. The number of runoff curves and field water-holding capacity had a considerable influence on the uncertainty of the runoff simulation. Furthermore, the number of runoff curves, terrain factor, soil erodibility factor, tillage management factor, soil and water conservation factor, and chemical fertilizer application amount had considerable influences on the uncertainty of sediment, nitrogen, and phosphorus load calculation. The number of runoff curves had the most significant effect on the uncertainty of the model output, which indicated that the runoff generation process is the driving force of erosion and transportation, affecting sediment and the runoff of various nutrients. The uncertain parameters of sediment and nitrogen and phosphorus were consistent, which indicated that the sediment was the carrier of nitrogen and phosphorus output. In short rainstorm events, the forms of nitrogen and phosphorus output were overwhelmingly dominated by the sediment-bound state, and the uncertainty of sediment directly affected the accuracy of nitrogen and phosphorus output. The uncertainty of the sediment in the model output was the largest and the runoff uncertainty was the smallest. On the basis of these results, we conclude that simulation of hydrological and soil erosion processes is a key factor contributing to model calibration and uncertainty reduction. To control and manage soil erosion and non-point source pollution, the number of runoff curves, fertilizer measures, farmland management, and soil and water conservation should be considered. |
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