Watershed Boundaries
November 2017 –
We all live in a watershed. In Polk County we start in the Upper Mississippi watershed and are sub-divided into smaller area units. The USGS HUC 8, HUC 10, and HUC 12 watershed boundaries have been added to the Polk County Auditor GIS website to help visualize the location of watersheds within our county.
You can view the watershed boundaries at https://apps.polkcountyiowa.gov/GISMapping/MapViews/View/3214
Learn more about watershed basics at the Iowa DNR site
Iowa DNR pamphlet watersheds 101
The Watershed Boundary Dataset (WBD) defines the areal extent of surface water drainage to a point, accounting for all land and surface areas. Watershed Boundaries are determined solely upon science-based hydrologic principles, not favoring any administrative boundaries or special projects, nor particular program or agency. The intent of defining Hydrologic Units (HU) for the Watershed Boundary Dataset is to establish a base-line drainage boundary framework, accounting for all land and surface areas. At a minimum, the WBD is being delineated and georeferenced to the USGS 1:24,000 scale topographic base map meeting National Map Accuracy Standards (NMAS). Hydrologic units are given a Hydrologic Unit Code (HUC). For example, a hydrologic region has a 2-digit HUC. A HUC describes where the unit is in the country and the level of the unit.