Abstract:The impact of critical source area (CSA) and DEM resolution on hydrological attributes was examined by comparing seven sets of CSA (0.5, 1, 2, 3, 4, 6, and 8km2) and eight DEMs (30, 40, 50, 60, 70, 80, 90, and 100m) using the case study of Dage sub-watershed of Chaohe watershed of North China. The accuracy of agricultural nonpoint source pollution models (AnnAGNPS) stimulation on runoff, sediment and nutrient loads on these different sets of CSA and DEM was further suggested. Variation of CSA would lead to the uncertainty of average slope which increase the generalization of land characteristics. At the range of CSA from 0.5km2to 1km2, there was little impact of CSA on slope. Runoff amount did not vary so much with the variation of CSA whereas soil erosion and TN load change prominently. An increase of sediment yield was observed firstly then a decrease following later. Evident decrease of TN load occurred, especially when CSA was bigger than 6km2. TP load showed little variation with the change of CSA. So the proper CSA was the basis of AnnAGNPS Model simulation. Regarding to the impact of DEM resolution within an AnnAGNPS Model simulation, there was significant impact on slope gradient which can be corrected by cubic model with the correction of 99.80% based on the liner regression equation of average slope and DEM mesh size. Runoff did not vary much with decrease of DEM resolution whereas soil erosion and total nitrogen (TN) load change prominently. There was little effect on runoff simulation of AnnAGNPS modeling by the amended slope using an adjusted 50m DEM. A decrease of sediment yield and TN load was observed with an increase of DEM mesh size from 30m to 60m; a slight decrease of sediment and TN load with the DEM resolution bigger than 60m. There were similar trends for total phosphorus (TP) variation, but with less range of variation than the simulation of sediment, TN, and TP. In all, the amended simulation still had a large difference relative to the results using 30m DEM. Results for Dage sub-watershed showed that fine meshes were desired to avoid large underestimates of sediment and total nitrogen loads and moderate underestimates of total phosphorus loads. Decreasing the mesh size beyond this threshold did not substantially affect the computed runoff flux but generated prediction errors for nitrogen and sediment yields.
王晓燕, 林青慧. DEM分辨率及子流域划分对AnnAGNPS模型模拟的影响[J]. 中国环境科学, 2011, 31(增刊): 46-52.
WANG Xiao-Yan, LIN Qing-Hui. The effect of DEM resolution and subwatershed delineation on AnnAGNPS model simulation. CHINA ENVIRONMENTAL SCIENCECE, 2011, 31(增刊): 46-52.