The USGS website
Purpose: To practice delineating a watershed, and to consider methods for estimating the area of a watershed.
Problem: Watersheds are the fundamental hydrologic unit for managing water resources. NYCDEP supplies
and manages drinking water from three watersheds within upstate New York, the Croton, Catskill, and
Delaware watersheds. Prior to developing these water supply systems, engineers had to delineate the
watersheds (area of land that drains water from precipitation into water bodies). Watershed delineation allows
engineers to estimate the area of drainage.
You will be completing these same tasks for a small watershed in Tafton, PA. Please complete the delineation
by hand using a topographic map and then estimate the area of this watershed online by using computer
Go to the USGS website (or MyTopo, or another reliable and free topographic map source) to
preview/download a free topographic map at: http://www.usgs.gov/pubprod/. Click on “Map Locator &
In the Search box, type “Tafton, PA” then click “Go.”
Click on the red marker. This should bring up a series of files. Select the “Hawley US Topo” for the year 2016,
7.5 minute by 7.5 minute (27Mb file).
Download to your laptop or desktop, and print a copy of the topographic map. *Suggestion: Zoom in to Tafton
on the map and print the “current view” under “Pages to Print…More Options.”
Delineate the drainage area for “Fairview Lake” and “Mainses Pond” using “Fairview Lake Outlet” as the point
of interest (PI). Use the steps discussed in class to delineate the watershed. *Suggestion: It may help to do this
in pencil first and then go over it in colored pencil, pen or thin marker using different colors to show the steps in
Estimate the drainage area in acres. Go online and look up Google (ACME) Planimeter, use this computer
software as your method for estimating the watershed area in acres. First, locate Tafton, PA and then make
sure to select the USA Topo layer. Add markers/points to depict your Mainses Pond delineation. Once all
markers/points connect, Planimeter displays the measurement of the drainage area in acres at the bottom of
the map. Save (take a screenshot or print and scan) your completed measurement to submit with your
homework. Save a copy of this to your computer, you will need to use this specific Planimeter estimation again for our next homework and in lecture.
Submission: Each student is required to submit two documents, along with a cover sheet, to Blackboard.
Include your full name, class name, homework number, and the date on a cover sheet. With your cover sheet
you should submit:
A scanned copy of the printed Tafton, PA topographic map that includes your hand-drawn watershed
2/20/2021 Order 337154650
delineation, using Fairview Lake Outlet as the PI.
A copy of your Planimeter estimation of the same watershed area (this can be printed and scanned or a
screenshot photo). Planimeter should display the estimated area of your watershed in acres at the bottom of
your delineation, please highlight or circle this number.