不同精度的土壤数据对水质和水量模拟的影响

【背景】模型模拟是研究面源污染的重要手段,建模过程中输入数据的质量是影响模型准确度的重要因素,其中土壤数据作为流域模型的重要输入数据之一,对模型的产流过程有重要的影响。然而,以往的研究多集中于土壤数据精度对水量和水文过程的影响,对水质的研究还比较欠缺。【目的】为丰富该领域建模的先验知识,为流域模型建立过程中的数据选择提供帮助。【方法】采用SWAT（soil & water assessment tool）模型,利用不同精度（1:5万、1:50万和1:100万）的土壤数据进行建模,对凤羽河流域的水量、泥沙、总氮和总磷含量进行了模拟。并采用SWAT-CUP软件进行参数的率定,得到基于3种不同土壤数据的最佳模拟结果。在此基础上,研究不同精度土壤数据对水文响应单元划分、模型参数、水质和水量模拟的影响。【结果】（1）土壤数据对水文响应单元（HRU,hydrologic response unit）的划分数量有明显影响,HRU划分数量的敏感性与划分阈值及土壤图详细程度有关;（2）进行参数率定后模型的表现效果有明显的提高,不同精度的土壤数据对于不同指标（流量、泥沙、总氮和总磷）的模拟效果存在差异,但并非土壤数据精度越高模拟效果越好;（3）随着子流域面积的增大,不同土壤数据提取的土壤属性的平均值趋于一致,且校准过程会对面积较小的子流域产生较大的影响。【结论】因此,在实际的模型模拟中应根据流域的大小和模拟的指标选择土壤数据的精度,同时在模型校准过程中要注意空间尺度的影响。

Impact of Soil Data with Different Precision on Water Quality and Flow Simulation

【Background】 Watershed model is an important tool to study non-point source pollution, and the reliability of input data is an important factor to ensure the accuracy of the model estimation. Soil data, as one of the important input data of the watershed model, has a significant influence on the runoff process. The previous studies mainly focused on the water quantity and hydrological process, while the research on water quality needs more attention. Furthermore, the disagreements over appropriate resolution of the soil maps also existed in the previous studies. 【Objective】 The purpose of this study was to enrich the prior knowledge of modeling and to provide useful suggestion for data selection in watershed simulation. 【Method】 This paper employed the widely used SWAT (soil & water assessment tool) model as an example and simulated flow, sediment, TN (total nitrogen) and TP (total phosphorus) of Fengyu river basin by three types of soil data with different scales. The scales were used for soil data as follows: 1﹕50 000 (soil-1), 1﹕500 000 (soil-2) and 1﹕1 000 000 (soil-3). SWAT-CUP software was used to adjust parameters. Based on the above methods, the effects of soil data with different scales (1﹕50 000, 1﹕500 000 and 1﹕1 000 000) on HRU (hydrologic response unit) division, model parameters and water quality and quantity were studied. 【Result】 (1) Soil data with different scales had great influence on the result of the HRU division, and the sensitivity of the number of HRU division was related to the division threshold and soil map precision. (2) The calibration of model parameters could remarkably improve the simulation performance of the model. The simulation performance associated with simulated substance, and the highest precision soil map not had the best simulation performance. (3) The attributes of soil tended to be consistent with the increase of sub-watershed area. The variation of simulation results caused by different soils gradually tends to be steady with the increase of confluence area, and the calibration process could have a great effect when confluence area was small. 【Conclusion】 In summary, the precision of soil data should be selected according to the basin size and simulated substance, and the impact of spatial scale need to be considered.