SWAT模型土壤空间离散化对径流和输沙模拟结果的影响

以东江源为研究区，采用SWAT （Soil and Water Assessment Tool）模型，通过设置11种子流域划分方案，并保持土地利用和地形2个要素不变，以定量分析子流域划分引起的土壤离散化对产流产沙过程的影响。结果表明：（1）随着子流域数量的增加，土壤类型空间离散化趋势越明显，其中面积最大的泥红壤面积显著减少（P<0.05），面积第2和第3的渗育质水稻土和黄壤显著增加（P<0.05），面积最小的石质土在子流域数量少（11~267个）时该地类被概化完全消失，子流域数量增加到524个后，该地类面积呈增加趋势（P<0.05）。（2）土壤空间离散化导致年均径流量（1.32%）和输沙量减少（P<0.05），且对输沙量影响更显著（18.07%，P<0.01）。（3）随着土壤离散程度增加，年平均最大1天、连续最大5天、连续最大7天输沙量均显著减少（16.64%，17.54%，17.34%，P<0.01），而径流量变化不显著（0.59%，0.89%，0.83%，P>0.05）。（4）土壤空间离散化导致洪水过程输沙量峰值显著减少，而对洪峰径流量影响并不显著。子流域划分引起的土壤离散化主要通过土壤侵蚀因子K值变化而引起输沙量变化。研究结果将为分布式水文模型不确定性研究和提高模拟精度提供参考。

Effect of Soil Parameter Spatial Discretization on Runoff and Sediment Transport Simulation Results in SWAT Model

Dongjiang River Basin was selected as the study area, which is located in the south of Jiangxi Province, China. The SWAT model was used to evaluate the influence of different watershed delineation on runoff and sediment yield. Eleven scenarios including the sub-watershed thresholds were 25, 50, 100, 200, 400, 800, 1 100, 1 500, 2 000, 3 200, 4 000 hm², were used to analyze the impact of soil spatial discretization on runoff and sediment yield. Terrain and land use data were input a single terrain and soil data to fix the effect of terrain and soil data spatial discretization. The results were as follow: (1) The discretization effects of soil parameter significantly increased with the increasing of sub-watershed, the largest area of latosol reduced significantly (P<0.05), the second largest area of osmotic paddy soil and the third largest area of yellow soils increased significantly (P<0.05). Lithosol soil, the smallest area soil type, was totally disappeared by soil discretization when the number of sub-watershed was under 267, while it increased when the number of sub-watershed was more than 524 (P<0.05). (2) The spatial discretization of soil parameters reduced the annual runoff (1.32%, P<0.05) and annual sediment yield (18.07%, P<0.05), and the sediment yield decreased greater than annual runoff. (3) The annual maximum one-day, annual maximum five-day, and annual maximum seven-day sediment yield decreased significantly with the increase of delineation degree (16.64%, 17.54%, 17.34%, P<0.01), while the sub-watershed delineation had less influence on the annual maximum one-day, annual maximum five-day and annual maximum seven-day runoff yield (0.59%, 0.89%, 0.83% P>0.05); (4) The peak sediment yield decreased significantly with the increase of delineation degree, while the effect for peak runoff was not significant. The soil parameters spatial discretization of watershed subdivision mainly affected the change of sediment yield through the change of K-factor. The research results will provide reference information for the selection of optimal computing units, improving the simulation accuracy and reducing the uncertainty of model simulation.