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Maps By Mitch

Watershed Gerrymander

June 11, 2012

Welcome to "Maps By Mitch". A "blog" of sorts to highlight various maps and the techniques used to create them. I hope to have a new "map" posted on a monthly basis.

This month’s map comes from a gentleman who approached me last month and asked a very intriguing question: what would the Pennsylvania counties look like if they were to be based on watersheds rather than demographics? Presently, this question was prompted by the difficulty to manage water resource projects in Pennsylvania. This is because a single watershed may span multiple counties. After some discussion with the gentleman, I decided to take this idea and create a correlating map.

First a little background on PA watersheds. Pennsylvania is comprised of six main watersheds with a Hydrologic Unit Code (HUC) 4. They are: Delaware, Erie, Genessee, Ohio, Potomac and Susquehanna. As HUC numbers increase, the size of the watershed decreases. For instance, a HUC 6 watershed contains fewer square miles than a HUC 4 watershed. The data used for the maps contains HUC 4 and HUC 10 watersheds.

The map at the top of the page shows PA’s HUC 4 watersheds, shades of blue, with the current county boundaries. The lower map shows a rendition of what the counties may look like if based on HUC 10 Watersheds. This map was created by merging HUC 10 watersheds together in order to encompass a major river and its tributaries. Therefore, no tributary from one HUC 10 (county) enters any other county.

This map was created using data collected from the Pennsylvania Spatial Data Access (PASDA) website and I wish to thank Eric Jespersen from Fisher Associates for his insight and help with this project.

Click on the map for a PDF (3.7 MB).


6/12/2012 1:53:17 PM
Question, what does the application of HUC 4 to HUC 10 have to do with county boundaries? Demographics currently used did not change the location of county boundaries just the legislative district boundaries.
I guess I don't get the connection. :)

7/13/2012 3:07:44 PM
The maps are simply a device to illustrate some of the difficulties and inconsistencies in creating and enforcing public policy regarding floodplain and stormwater management. The regulations were initially separated in 1978 through passage of Acts 166 (Floodplain) and 167 (Stormwater). Regulations developed over time are enforceable at municipal and County levels, so that to treat any large watershed consistently requires the involvement and concurrence of many jurisdictions.

7/16/2012 7:24:55 AM
Water is indispensable nutaral resource for human and other lives. But agricultural pollutants diminishing the freshwater resource and destroying the aquatic habitats not only in the USA but also in many other parts of the world like Bangladesh . The agricultural as well as industrial and urban pollutants flowing down to the rivers and then to the Bay of Bengal and thousands of flora and fauna are at a risk of destruction. So immediate attention should be given on right type of agricultural practice with right crop at right place with right cultural practice.

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