基于三级汇流和产输沙结构的分布式侵蚀产沙模型

黄土丘陵沟壑区面临严重的土壤侵蚀问题,是黄土高原主要产沙区域,针对该区域的土壤侵蚀产沙模拟一直是黄河泥沙研究的热点。尽管如此,已有侵蚀产沙模型对坡面、沟壑侵蚀环节刻画并不完善,沟壑侵蚀过程的忽视限制了模型在沟壑区侵蚀产沙模拟的精度。为此,本文考虑了沟壑侵蚀的特殊性,从分布式水循环模型(the Water and Energy Transfer Processes in Large River Basins,简称WEP-L)的"坡面-河道"二级产汇流结构中单独分离出沟壑环节,提出了"坡面-沟壑-河道"的三级汇流和产输沙结构,从而构建了基于WEP-L的分布式侵蚀产沙物理模型(WEP-SED)。将WEP-SED应用于无定河流域白家川水文站控制区,模型得到的白家川1956—2010年月均输沙率过程与实测过程接近。结果表明,WEP-SED可有效应用于黄土丘陵沟壑区的侵蚀产沙模拟研究。此外,模拟的白家川沟壑环节多年平均侵蚀量约占该区域总侵蚀量的49%,且94%的沟壑侵蚀集中于7—9月。模拟结果充分说明该区域沟壑侵蚀的严重性,细化沟壑侵蚀过程对于提高该区域侵蚀产沙模拟精度具有重要意义。

A distributed soil erosion model based on the three-process of runoff and sediment transport

Most sediments on the Loess Plateau in Yellow River basin come from the gullied rolling loess regions,where severe erosion problems attract significant attention for various soil erosion studies. However, nearly all the soil erosion models applied to these regions only consider the slope and river erosion processes. The absence of gully erosion process significantly limits their application. Therefore, in terms of the unique features of the Loess Plateau, this paper develops a three-process-based distributed soil erosion model (WEP-SED) to investigate soil erosion based on the Water and Energy Transfer Processes in Large river basins (WEP-L). In the WEP-SED, a sequential "slope-gully-river" structure is built by separating the gully process from original river process of "slope-river" in WEP-L. The proposed model is applied to the Baijiachuan hydrological station in the Wuding River basin. The simulated monthly average sediment transport rate from 1956 to 2010 is pretty good with the correlation coefficient (R) of 0.80,Nash-Sutcliffe Efficiency (NSE) of 0.63 and relative error (RE) of -5.23%. The simulation results demonstrate the applicability and efficiency of WEP-SED. Furthermore, the simulated average annual gully erosion attains a ratio of 49% to the total soil erosion,and more than 94% of gully erosion occurs in several months from July to September,which justifies that it is of great significance to separate the gully erosion process during soil erosion modeling in the gullied rolling loess regions.