Watershed Delineation
A USGS marker on mapping software of a delineated watershed in VirginiaCopyright 2021 Rachelle Rasco, Virginia Tech RET
Understanding watersheds can help engineers design systems that deliver or protect key sources of water. In this activity, students become civil engineers as they use topographic maps to delineate watersheds. Watersheds show the path water travels over land in a particular area on its way to a river, lake, or stream. Defining the boundaries of a watershed is important for determining the amount of runoff that can come from that area into the river, lake, or stream. The boundaries also help to identify sources of pollution that could mix in with that runoff as it passes over the land area.
Civil engineers must be able to estimate the quantity of water that could leave a watershed when sizing bridges, culverts, and stormwater pipes. They also use this information to design stormwater facilities that will buffer peak flows that would cause flooding due to runoff. Recently, more requirements have been made about the levels of nutrients allowed to leave a developed site, so sites also need to be designed to limit and remove nutrient loads that could be carried in the runoff. Being able to define the watershed and the sources of water in that area are necessary and are the first steps to planning for and mitigating runoff from a watershed.
After this activity, students should be able to:
- Delineate a watershed using a topographic map.
- Delineate a watershed using USGS StreamStats.
- Determine some characteristics of a watershed.
- Determine direction of streamflow using a topographic map.
- Build a report of watershed characteristics.
- Present data succinctly to an audience.
- List 5-10 characteristics of streams in their area.