并且，由于它们是在地下形成的，而不是由地表水流形成，所以并不是所有的通道都有通向外部世界的开口。
And, since they were created underground and not from flowing surface water, not all these passageways have an opening to the outside world.
根据DEM数据，确定了汤旺河流域的地表水流方向、集水区的划分及水系网络空间分布特征。
On the base of the DEM, the spatial distribution of flow directions, watershed boundaries and stream networks of Tangwanghe Catchment were studied.
基于田间实测的地表水流推进过程，利用水量平衡法推求波涌灌溉间歇供水条件下的土壤入渗参数。
Based on water flow advance data observed in fields, infiltration parameters under surge water application were determined with water balance method.
DRASTIC方法可以进行地下水污染的脆弱性评价，但是却没有涵盖风险的概念，也忽视了污染物随地表水流运动的动态特性。
The DRASTIC method can provide groundwater vulnerability to pollution but does not contain risk concept and ignore hazard's dynamic nature of water movement.
采用GIS的方法，建立了环县数字高程模型（DEM），研究了本区地表水流方向、集流能力、子集水区的划分及水系网络空间分布等水文特征。
By means of GIS method, the digital elevation model(DEM)is established, the flow direction, flow accumulation, subcatchment boundaries and stream network spatial distribution are studied.
正如她所说，她的家在加纳市区，“在那里，任何地表水都是开源污水流。”
She makes her home in urban Ghana where, as she describes, "Any surface water is an open sewage stream."
正如她所说，她的家在加纳市区，“在那里，任何地表水都是开源污水流。”
She makes her home in urban Ghana where, as she describes, "Any surface water is an open sewage stream."
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