Different Scale Digital Elevation Model Extraction Of The Water System Of The Scale Effect

Always being one of the central issues of hydrology and geography, scale is classified into three categories: spatial scale, temporal scale and attribute scale. At present, the researches of scale in hydrology are mainly on spatial scale and temporal scale while attribute scale is rarely researched. And in accordance with different scales water movement law, research methods and model establishment vary greatly. So the scale factor is noticeably restrictive.With the introduction of "3S" technology to water science, hydrologic research not only makes great progress in data acquirement, model establishment and range of research field, but also lays physical foundation for hydrology research above the drainage scale, which is accordingly brought closer to objective reality. Distributed hydrologic model based on digital elevation models (DEM) is one of representations. However, attentions are usually focused on the establishment of model, neglecting the researches on essential construction feature of stream networks, especially the law of change caused by resolution and mapping scale of DEM, which results in the insubstantial foundation for the establishment of model and makes it less scientific and adaptable. At the same time, all related researches are based on watershed and region scale, which require different spatial and temporal resolution of data source in order to match data and model in scale and parameter structure. At last, digital drawing, spatial data integration etc require research on law of change of streams under different scales. But the related researches are few.This research subject originates from the item of State Natural Science Fund (49971065)--"Research on the Uncertainty of DEM and its Influences on Application" . This treatise,Whose theme is scale effect by employing DEM of different scales to derive stream, studies the law of stream construction (Horton laws) and general features (stream networks fractal) through comparison and analysis of derived stream from DEM of different scales in Jiu Yuangou watershed in Northern Shaanxi province, and tries to find out the influences of scale on deriving stream, the law of stream construction of hilly and gully region in loess plateau , and the law of scale's influences on the fractal dimension of stream networks.Because many related theories and technologies are still on trial, many points in thistreatise are just personal views. Innovations of this treatise are reflected in the following several aspects, namely, 1) Overview systematically the current situation and problems of stream research, and put forward the ideal of doing stream research with GIS. 2) Overview current situation and problems of stream networks fractal research, and put forward the way to research stream networks fractal and dimension with GIS. 3) Try to find out the influence of scale on stream through comparison and analysis of derived stream from DEM of different mapping scale and resolution. 4) Inquire into influences of scale on the fractal dimension of stream networks and find out that stream is complicated fractal in essence.