|DNR Catchments: New Watershed Data for Minnesota
By Sean Vaughn, GIS Hydrologist, MN-DNR Waters
After nearly eleven years of development, the Minnesota DNR Division of Waters – Watershed Delineation Project (DNR-WDP) has released a new base-watershed dataset for Minnesota. This dataset consists of over 10,000 polygon watershed delineations in one, statewide, seamless dataset called the Minnesota Department of Natural Resources Catchments (DNR Catchments). DNR Catchments represent the smallest delineated and digitized drainage area mapped by the DNR-WDP.
The overall goal of this data development effort is to produce the best watershed delineations available that reflect the current hydrology of the landscape as interpreted from as many data sources as is necessary to derive acceptable drainage area delineations.
DNR Catchments represent the hydrologic boundary that contains the land area (including all water features) upstream from or between DNR Pour Points. These pour points represent the location where concentrated water discharges from a DNR Catchment polygon. A pour point can represent a discrete water control entity (e.g. dam, gage) or generalized area of hydrologic impediment (e.g. channel constriction, culvert) that influences and/or monitors surface water characteristics and/or the surface elevation of a hydrologic resource.
Minnesota DNR Catchments are not scale dependent, that is, there are no minimum or maximum mapping unit size criteria for catchment delineations. An individual DNR Catchment may represent the drainage area of a 1-acre prairie wetland, a 500-acre recreational lake or the land area between two other DNR Catchments.
The DNR-WDP methodology is unique because it incorporates three techniques: traditional on-paper; modern on-screen; and GIS-automated delineation into one comprehensive methodology. The merging of these three techniques evolved into a complex, iterative process of heads-up on-screen digitizing. The procedure utilizes as many as 30 different datasets, sources of information and field reviews. Primary data sets used for catchment delineation included 1991 USGS DOQ’s and 2003-2004 FSA Imagery (both 1-meter ground resolution), DNR hydrologically-corrected DEM’s and USGS 1;24,000 DRG’s. The final product is best described as a manually derived, human-interpreted, "off-site" height of land watershed delineation developed and maintained using GIS technology.
These new DNR Catchment delineations will facilitate projects related to hydrology and hydrologic design, watershed assessment, water quality and clarity, fish and wildlife management and GIS analysis. Used alone or as a system of upstream – downstream drainage areas, Minnesota DNR Catchments are the elementary drainage "building blocks" used to derive watersheds and hydrologic units of various sizes.
The Minnesota DNR Catchment dataset is the maintenance version for all watershed delineations in Minnesota. The DNR Catchment delineations were developed to create a base dataset from which other statewide Minnesota DNR Watershed datasets are derived. DNR Catchments share coincident boundaries that combine (dissolve) to define the commonly-used DNR Major and Minor Watersheds, as well as DNR Basin Watersheds (Lake Watersheds). DNR Catchments will also be combined to create Minnesota DNR Level 01 (HUC 02) through Minnesota DNR Level 06 (HUC 12) watersheds. These units correspond to hydrologic unit delineations defined nationally by the United States Geological Survey and the Natural Resources Conservation Service within the Watershed Boundary Dataset.
Only the DNR Catchments are currently available. Other statewide DNR watershed datasets derived from the DNR Catchments and DNR Pour Points will be published in the coming weeks.
The DNR Catchment dataset can be found on the DNR Data Deli in the Hydrography section of the Data Catalog. The descriptive distribution name is DNR Watersheds - DNR Level 08 - All Catchments. The dataset is named wshd_lev08py3.
Further information about this dataset is available via the metadata and an online report or by contacting:
Sean Vaughn, GIS Hydrologist
DNR Waters - Watershed Project Data Manager