基于ArcGIS和SWAT的山区、平原区复合地貌流域划分方法研究

A watershed delineation method for mountains,plains complex landform area based on ArcGIS and SWAT

流域划分是研究区域水量平衡的基础和前提。山区和大平原区流域划分的技术已较为成熟,但在山区、平原区复合的复杂地形地貌特征区域,流域划分方法仍处于探索阶段。该地区陆面水文循环过程复杂,地表水和地下水相互补给关系密切,单以山区流域划分技术平原区流域划分技术无法完整的划分出研究区所在的全流域,进而导致流域内水文循环体系不完整。选择典型代表内蒙古河套灌区流域为例,综合山区山脊线、天然河流和灌域边界来进行流域划分,提出了采用修正系数处理平原灌区小地形起伏,依据灌溉排水系统重新划定子流域和结合土地利用图确定山区、平原复合地貌区边界的综合处理技术。划分结果表明,研究区河网拟合度高,水文循环单元符合用水管理特点,复合地貌区山区流域面积占总流域面积的58.1%。在以全流域尺度计算区域内水量平衡时,山区流域面积不能忽略。该方法的成功应用为灌区流域内的供水用水平衡及农业施肥对下游污染研究提供基础。同时也为其它具有相似地貌类型的地区流域划分提供思路和参考。

Watershed delineation is the basis for studying the hydrological cycle with the distributed hydrological model. The process of runoff from mountains and plains is very simple;the watershed boundary delineation is based on natural dividing crest,irrigation ditches or administrative boundaries in plain areas. All of the watershed delineation methods in the mountain and plain areas are relatively effective. But in the compound mountain-plain landform areas,surface water cycle process is rather complicated,especially in areas with strong human activity,which are compound artificial-natural hydrological cycle types,the existing watershed delineation technology can not be used to define the whole basin. This paper provides a systematic method to resolve the problem. In the plain area,the DEM is preprocessed with the correction coefficient and is based on the DEM＂Burn-in＂elevation increment methodologies. In the mountains,the watershed boundary is delineated with D8 algorithms of the module in the SWAT model. Finally,the regional land use map was adopted to complete the whole watershed and sub-basin delineations. In the case of Hetao Irrigation District,Inner Mongolia,China,the delineated watershed boundary is composed of the mountain ridge,the boundary of irrigated lands and a natural river. This method has proved to be correct and feasible. The results show that the river network and drainage channel system are highly fitted with the real objects,the hydrologic cycle is consistent with actual water management units,and the area of watershed in the mountain area account for 58.1% of the total watershed area. It also shows that the division of the whole basin is a precondition for using the distributive hydrological model to study regional water balance.Water from the mountain sub-basins should be a large contributor to the whole basin and the sub-basins in the mountain area cannot be ignored when calculating water balance in the plain area. The watershed delineation method proposed in this paper can be used as a reference in similar topographic regions by using this model.Moreover,high-resolution DEM and detailed land use maps are an effective means to improve watershed delineation precision.