Water Resources - Historic Streams

This is the Department's legacy master stream coverage. The last updates to this layer occurred in late 2004. This layer has been replaced by the High Resolution National Hydrography Dataset (NHD) and as such should only be used to aid in identifying legacy stream codes. This layer was digitized at a scale of 1/24,000. All streams are connected and have flow direction. Each stream is identified by a unique 5-digit stream code found in the WRDS (Water Resource Data System) field. The streams are further divided into segments. The first stream segment flows from the headwaters to the first tributary. Subsequent segments are tributary to tributary. The final segment flows from the last tributary to the mouth which for purposes of this data layer is defined as the point at which the stream crosses the Pennsylvania boundary. The unique segment identifier is constructed from three concatenated fields. The stream code, downstream river mile, and finally the upstream river mile of the segment boundaries (12345_8.000_ 12.000). The river miles are measured from the mouth, at the Pennsylvania boundary, upstream to the headwaters.

本数据集为本部门遗留的主河道覆盖图层。该图层的最后一次更新于2004年末完成。此图层已被高分辨率国家水文数据集（High Resolution National Hydrography Dataset, NHD）取代，因此仅可用于辅助识别遗留河道代码。本图层的数字化比例尺为1:24000。所有河道均已连通并带有流向信息。每条河道均由水资源数据系统（Water Resource Data System, WRDS）字段中的唯一5位河道代码标识。河道进一步被划分为多个河段，首个河段从河源流向第一条支流，后续河段均为支流间的衔接段，最后一段河道从最后一条支流流向河口，本数据图层中将河口定义为河道穿越宾夕法尼亚州州界的点位。唯一的河段标识符由三个拼接字段构成，依次为河道代码、河段边界的下游河道英里数以及上游河道英里数（示例格式：12345_8.000_12.000）。河道英里数以位于宾夕法尼亚州界处的河口为起点，向上游河源方向测算。