Using GIS to Determine Extent of Gauged Streams in a Region

A geographic information system (GIS) based approach to quantify the coverage provided by a stream gauge network is presented. This approach relies on digital elevation models, a digital representation of the observed stream network, and the locations of all stream gauge locations in the area of interest. A case study examining the coverage provided by the U.S. Geological Survey gauge network in the state of Maryland is presented. The reported coverages corresponding to an observed stream network at 1:100,000 map scale are 8.1% for all gauges in the region and 4.7% considering only active gauges. The apparently low coverage afforded by the gauge network is explained against the observation that the areal coverage of the gauge watersheds is far greater than the reported gauged stream extent. This work highlights the frequent misconception that the gauged property of streams pertains to all streams within the gauge watershed. In reality, this property is a one-dimensional characteristic pertaining only to the stream in the vicinity of the gauge. Issues of map scale and decision making regarding the addition or removal of stream gauges are also addressed.