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The hydro network is a highly useful data structure for supporting hydrologic analysis. During the three-year design process for Arc Hydro, researchers at the Center for Research in Water Resources built stream networks for each of 23 river and coastal drainage basins of Texas. This experience convinced us that Arc Hydro users needed more control over flow direction on HydroEgeds than is available in the automated flow direction assignment process using network analysis tools in ArcGIS.
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为什么水文观测站采用建立relationship的方式来和network关联？（更加直观的方法是，直接把点点在networking上）
This process has the advantage of leaving point features at their true x,y location and not forcing them to be located exactly on the network line (only the related junction must be on the network).