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Stream Gages and GIS

Brian C. Welch, St. Olaf College, Northfield, MN
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This material is replicated on a number of sites as part of the SERC Pedagogic Service Project
Initial Publication Date: September 18, 2006 | Reviewed: October 22, 2012


This exercise utilizes the national network of stream gage data provided by the USGS Water Resources Division as an online Geographic Information System (GIS). The presentation of real-time stream flow data national and state maps presents opportunities for students to interpret recent regional-scale climate events based on current stream flow, monitor changes in time, and to consider additional interpretations that could be derived if other data were in map form.

Connections are provided to existing online hydrology exercises that consider interpretations based on time-series stream flow data from single gages within the USGS database. This exercise may be used to consider regional-scale conceptual problems in tandem with the traditional hydrology exercises, or vice versa.

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Learning Goals

  • Develop map interpretation skills
  • Introduce the concepts of spatial data organization and presentation to familiarize the students with the basic ideas of GIS
  • Consider spatial and temporal relationships within a large network of stream gages
  • Consider the relationships between recent or seasonal meteorlogical/climate events and regional climate characteristics and surface hydrology

Context for Use

This exercise provides material to consider the spatial relationships seen within the database through the online USGS GIS interface. There are numerous exercises available through the SERC/DLESE and other web resources that make a variety of hydrologic interpretations based on stream gage time-series data (e.g. stream response to melt/precipitation events). Thus, the exercise can be considered as a stand-alone activity, or used in tandem with the more traditional hydrology exercises.

Teaching Materials

Hydrology Exercises Using USGS Stream Flow Data

Teaching Notes and Tips

The GIS aspects of the USGS water data site may be incorporated into classroom discussions, homework or lab exercises, or exam questions. The important issue is to make the students aware of at least the following concepts:

  • The spatial hydrologic relationships within the real-time stream flow data presented in the online map
  • The possibilities for additional maps based on other data within the USGS database.
  • The temporal aspect of the real-time map and changes that might be anticipated based on meteorlogical, seasonal, and climate changes

The national map of real-time data color codes the station points as a measure of the current flow compared to the long-term flow statistics for the site. While individual sites may show anomalous flows due to relatively short-lived records, regional trends are generally accurate and representative of recent storm events, snow melt, or drought conditions.

Note on USGS website: The USGS site is generally quite reliable. Occasional state- or federal-level budget cuts may eliminate certain sites and equipment failures may interupt service. During winter months many of the northern and alpine gages will be frozen (indicated as "Ice" in the discharge report). Note that the automated sites may still produce fluctuating discharge graphs as the radio-sondes or pressure transducers respond to changing ice/snow/melt conditions. Historical stream flow data may contain multi-year gaps due to funding/mechanical problems.

The instructor can save maps of the national stream gage map or individual state maps on the due dates of the student assignments. These are useful for classroom discussions of the seasonal, meteorlogical, and climatic changes that caused the differences in stream flow seen in the maps.


For a classroom exercise (utilize classroom equipment): Break into small groups to develop interpretations about the real-time data map. Consider whether they are thinking about data presentation possibilities based on other data within the site.
At the start of the next class period, ask students to describe their hometown stream flow history as an informal writing assignment and/or quiz.

Incorporate GIS concept questions into a homework assignment after a classroom demonstration of the USGS website. Possible aspects of the assignment: Descriptions of reasonable weather/climate patterns that would produce the spatial distribution of stream flows seen on the website. Descriptions of new maps that could be made using other data from the website (e.g. peak historical flow). Consideration of national or site-specific temporal changes in flow after weather or seasonal events (e.g. hurricanes, spring melt).

References and Resources

Real-Time USGS Stream Flow Data for the Nation (more info) -- real-time data for the USGS stream gage network with map of current stream flow value normalized by the dailiy average flow.

Historical Stream Flow Data (more info) -- search page for historical stream flow data. The real-time data site provides map-based searches for specific stations. The station numbers can then be used in the historical data search.

The USGS Water Resources page -- the main gateway to water resource information from the USGS.