基于改进RUSLE模型的皇甫川流域土壤侵蚀产沙模拟研究

采用GIS与RS技术,以RUSLE模型为基础,增加流域输沙能力与淤地坝拦沙效率模块,并在黄土高原粗沙多沙区流域皇甫川进行验证。模型模拟结果显示:率定期1991-1999年皇甫站实测输沙量与模拟值拟合较好,纳什系数(Nash)与相关系数均超过0.7,而验证期2000-2009年的模拟结果相对较差。不同土地利用状况的土壤侵蚀模数表明:皇甫川流域土壤侵蚀模数超过15 000t/(km2·a)的区域主要发生于裸露的砒砂岩与植被覆盖较差的沙地;而土壤侵蚀模数小于2 500t/(km2·a)的区域主要分布在地势较为平坦的河滩地与植被盖度好的高原区。在相同降雨条件下,皇甫川流域不同土地利用类型土壤侵蚀模数的大小顺序为裸砒砂岩沙地耕地草地林地。根据修正RUSLE模型分析皇甫川流域淤地坝的拦沙效益发现,1991-2009年淤地坝平均年拦蓄泥沙约为0.42亿t,几乎与皇甫站(1955-2010年)年均输沙量0.41亿t相当。

A modified RUSLE model to estimate sediment yield in the Huangfuchuan watershed

We modified the Revised Universal Soil Loss Equation model(RUSLE)for soil erosion and sediment load simulation by making use of geographic information system and remote sensing techniques. The sediment transport capacity and check dam trapping efficiency modules were added to RUSLE model in order to compute sediment yield from soil loss data. The modified model was applied in the Huangfuchuan Watershed in the northern Loess Plateau as a case study. The simulated monthly sediment load showed good agreement with observations at the Huangfu station, with the Nash-Sutcliffe coefficient(NS) and correlation coefficient(R²)higher than 0.70 during 1991 to 1999 for model calibration;model verification from 2000 to 2009(no measurement data was available in 2005) displayed relatively worse results with a lower NS and R². Seasonal dynamics in sediment load can be well simulated in most cases;however,modeled sediment loads presented higher peaks than observation. This may be largely caused by model limitations and not considering detailed soil erosion processes. The most serious soil loss area with annual soil erosion modulus higher than 15 000t/km²/a mostly occurred in the Pisha stone and sandy region due to steep slopes and low vegetation cover. In the flat alluvial plain and high vegetation cover region, annual soil erosion modulus was less than 2 500t/km²/a. The annual soil erosion modulus with the same precipitation conditions,different land use types in the watershed can be ordered as:Pisha stone >sandy region >arable land >grassland >woodland. The results inferred that check dams in the Huangfuchuan watershed have trapped approximately 42 million t sediment,which is almost equal to the average annual sediment load at Huangfu station from 1955 to 2010.