站网密度和地形对模拟产流量和产沙量的影响

Impact of Network Density and Topography on Simulated Water and Sediment Yields

模拟计算中的误差可以归结为两个方面:一方面是输入资料的误差,这涉及到站网的密度、空间位置、测验仪器和流域内信息的时空分布;另一方面是模型算法、结构,这里涉及到确定性和随机计算方法所引起的误差。地形对降雨量、产流量和产沙量的影响及其估算是一个十分重要的课题,同时也是一个相当困难和研究基础十分薄弱的课题。本文选用与ArcviewGIS藕合的SWAT来分析站网密度和雨量站所处的空间位置对模拟产流量和产沙量的影响。以卢氏流域为研究区域,以卢氏24个雨量站的气象资料以及下垫面资料为模型的输入,分析站网密度和空间位置对产流量和产沙量的影响。研究表明:站网密度越小,计算的面平均雨量的误差越大;在水文模拟中,雨量站的多少有一个饱和的上限,当雨量站大于这个上限时,雨量站站的增加并不会增加模拟的精度;同样雨量站的站数有一个下限,在一定的模拟精度内,许可的最小雨量站。雨量站所处空间位置的高程值、坡度和坡向影响着模拟产流量和产沙量,在下垫面相同的条件下,迎风坡的雨量站模拟产流量大于背风坡产流量,坡度大模拟的产流量大;迎风坡模拟的产沙量大于面平均值,由于产沙受到降雨强度影响,背风坡的产沙量也有可能大于面平均值。

The errors of the hydrologic simulation can be attribute to two factors: one are the errors of the input data which includes the density of network, the location of the rainfall station and the space-time distribution of the hydrologic information of the simulation basin. The other factors are related to the structure, the compute method of simulation model. The impact of topography on the sediment yield and runoff generation is an important project and at the same time is an little studied problem. In this study the SWAT(Soil and Water Assessment Tool) coupling with Arcview GIS was used, and the Lushi basin were selected to investigate the impact of the network density and location of the rainfall station on the runoff generation and sediment yields. The results shows that the more sparse the network density,the larger the error of computed area-average rainfall. The density of network have a certain up limit and a low limit in the hydrologic simulation. When the number of the rainfall station exceeds the up limit or the below the low limit, the simulation results didnt changed much. The slope head to wind generated more runoff than the slope back to wind under the same underlay conditions. The steeper the slope the more runoff generated. The simulated sediment yields in the slope head to wind was great than the area-averaged sediment yields, but in the slope back to wind the simulated sediment yields may be large than the area-averaged sediment yields duo to the mechanism of sediment yields.