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Codes for the Identification of River Reaches and Watercourses in Minnesota

Title: Numeric Codes for the Identification of River Reaches and Watercourses in Minnesota

Date Issued: Approved by the Minnesota Governor's Council on Geographic Information

Who cares about this standard?

This standard is important to any public organization that collects uses or exchanges information about rivers, streams, and ditches in Minnesota.

When does it apply? When does it not apply?

This standard has been developed to improve the sharing and exchange of information about rivers, streams, and ditches in Minnesota. Use of this standard is mandatory when a state agency is transferring data to another agency, local government, federal agency, the private sector or a public requestor.

Use of this standard is recommended when local governments exchange data, or when new public data bases are being designed that require identification codes for river features. Use by local government, the private sector and the public is encouraged. This standard only applies to data that are being transferred and does not apply to how data are internally stored in a data base. It should be noted, however, that it is a long-term goal for everyone to use the same river reach and watercourse identification codes.

Purpose of this standard:

This standard describes two related concepts for identifying rivers, streams, and ditches in Minnesota. It brings together current state and federal river naming and identification practices into a common framework for data sharing and transfer. At the heart of this standard are two concepts:

  • 'reach', which is a segment of a stream, river, or ditch, generally defined from confluence to confluence, or by some other distinguishing hydrologic feature; and
  • 'watercourse', which can be composed of multiple reaches, is a named flowpath through a drainage network, from the source of a river to its mouth.

The 'reach' is designated as the primary standard, and is an acceptance by the state of Minnesota of the federal Reach Identification convention, as implemented in the EPA Reach files and in the newly-developed National Hydrography Dataset (a cooperative effort of the USGS and the USEPA).

The 'watercourse' is designated as the secondary standard, and recognizes the need of some state agencies for a single identifier for a river or stream throughout its entire length, and the need to formalize a single river identifier for state use.

The purpose of this standard is to provide a common coding scheme for identifying river reaches (including all or portions of rivers, streams, and ditches, and flowpaths through lakes and wetlands) and full watercourses in Minnesota, and for referencing locations along a river network. This standard enables the transfer of data among agencies and external customers. This standard can also improve the sharing of data among all participating organizations by avoiding duplication and incompatibilities in the collection, processing and dissemination of river-related data. This standard provides consistency with federal identification and naming conventions for rivers and streams, and promotes integration with national river database development and water quality data reporting, as well as data integration across state lines. It also allows the state to use federally-developed tools, most notably the Reach Indexing Tool, which creates a consistent river addressing mechanism which enables agencies to share information about events occurring at points or segments along a river.

Standard Requirements:


River Reach segments and identifiers have been defined nationwide by the United States Environmental Protection Agency. The EPA Reach designations have been adopted into the National Hydrography Dataset (NHD). NHD defines a Reach as a segment of surface water having a unique identifier. NHD describes the delineation of a reach as follows: The limit of a reach is a significant piece of surface water, generally defined as a stretch of stream between confluences or a lake. (Source: Standards for National Hydrography Dataset - High Resolution - National Mapping Program Technical Instructions. USEPA/USGS, DRAFT, October, 1998).

The Reach Identifier is a unique identifier composed of two parts:

  • Codes for the Identification of Hydrologic Units in the United States and the Outlying Caribbean Areas, Geological Survey Circular 878-A, 1982. (For Minnesota users, this hydrologic unit or HUC covers the same area as the DNR Major Watershed).
  • The final 6 digits are randomly assigned, sequential numbers that are unique within a Hydrologic Cataloging Unit. These are assigned during the creation of the EPA Reach file.

An example of the reach designation is as follows:

07040002002490, where07040002 is the Hydrologic Cataloging Unit Code for the Cannon River watershed in Minnesota, and 002490 is the reach or segment code for a portion of the Straight River. (The Straight River itself has multiple reach codes).

The provision of 6 digits for reach numbering ensures the ability to add new reach numbers to accommodate higher resolution data which will continue to add smaller streams to the system.

The U.S. Environmental Protection Agency has the authority for assigning Reach Identifiers and Reach Names, with names based on the USGS GNIS (Geographic Names Information System) database. GNIS is a digital compilation of all names that appear on the USGS 7.5-minute quadrangle map series. If there is a preferred local name, if the GNIS does not contain a name for a feature, or if the GNIS name is incorrect, there is a procedure in place in which the state can propose a name addition or correction to the USGS Board of Geographic Names. The DNR Division of Waters has responsibility for naming of water features in Minnesota.

National Hydrography Dataset (NHD) GIS data files for the state of Minnesota, which incorporate the reach numbering and naming convention, are available at scales of 1:100,000 and 1:24,000. Information about this dataset is available at

Note that this use of the term 'reach' describes an administrative unit based on a set of federal designations in the Reach Identification System. In a more generic sense, a 'reach'; is any segment of river defined for any purpose. Other agencies may define 'reaches' for their own management purposes which are independent of the federally-designated reach identification. For example, an agency may need to designate a portion of a river as a canoe route, a trout stream, a stream habitat improvement area, a fisheries survey investigation area, or a water quality study area. This Reach Standard does not override other agencies' needs to identify 'reaches' defined to meet their own specific purposes. In fact, the Reach Indexing Tool which is part of the National Hydrography Dataset toolset can be used to reference these agency-specific river segment definitions to the NHD dataset. This indexing works by referencing the user-defined reaches as percentage measures along the NHD reaches, and has the advantage of being scale-independent. This makes possible the easy exchange of data pertaining to these specifically-defined reaches, and enables them to be mapped easily.


A 'watercourse' is an aggregation of reaches to a commonly-recognized named feature. This is generally a river, stream, or ditch as named and represented on a map.

In the National Hydrography Dataset data model, a 'watercourse' is defined as a named path through a drainage network, which is essentially the length of a named river, stream, or ditch, from its headwaters to its mouth.

This is consistent with state definitions of 'watercourse'.

Minnesota Statutes 6115.0630 (Water Appropriation and Use Permits) defines Watercourse as:

Subp. 19. Watercourse. Watercourse means any natural, altered, or artificial channel having definable beds and banks capable of conducting confined runoff from adjacent lands.

Minnesota Statutes 6115.0170, (Protected Waters definitions) describes Watercourse in more detail:

Subp.41. Watercourse. Watercourse means any channel having definable beds and banks and capable of conducting generally confined runoff from adjacent lands. During floods water may leave the confining beds and banks but under low and normal flows water is confined within the channel. A watercourse may be perennial or intermittent.

Although a 'watercourse' in a generic sense could represent any portion of a flowpath, it is generally defined as the full extent of a flowpath that is named and recognized (e.g., the Cannon River, the Mississippi River, Minnehaha Creek, Judicial Ditch Number 14). As such it can have a name and identifier assigned to it. Watercourse then denotes the full extent of a named flowpath, from headwaters to mouth.

Note that, under this scheme, a small watercourse may be made up of a single reach. Larger watercourses are made up of many reaches or defined river segments. For example, the Cannon River is made up of 93 separate Reaches.

Watercourse numbering can be done according to either the state or the federal standard. There is a 1:1 correspondence between the state and federal standards.

Federal standard: Watercourse designation in the National Hydrography Dataset uses the federal watercourse identifier standard, which is the GNIS_ID, from the USGS Geographic Names Information System (GNIS) data set. The GNIS_ID is an 8-digit number (8C):


00659759 Minnesota River

00640946 Carver Creek

00640071 Bevens Creek

State standard: The state watercourse identification standard is the Kittle numbering system (Minnesota Stream Identification System), used by DNR Fisheries and Ecological Services. DNR Section of Fisheries staff use the Kittle Numbering System for all streams that they manage, and they intend ultimately to extend the system to all streams in the state. Reference for the Kittle numbering system is the DNR Section of Fisheries' MinnesotaStream Survey Manual, (Special Publication No. 120, April, 1978), and subsequent updates to this document.

Kittle is a compound identifier consisting of up to 10 parts, each designating another level of tributary. All stream numbers begin with a letter prefix indicating the main drainage basin into which they flow:

  • M = Mississippi River basin
  • S = St. Lawrence drainage basin (Great Lakes)
  • H = Hudson Bay drainage basin (Red and Rainy Rivers)
  • I = Iowa drainage

Within each of these major drainages, rivers were numbered, with each upstream tributary represented as an additional number, separated by a dash.

For example, Minnesota tributaries to the Mississippi River are numbered from the south boundary of the state upstream. The Mississippi itself is designated as M.


River Name Kittle Code

  • Mississippi River M
  • Minnesota River M-55
  • Blue Earth River M-55-76
  • Watonwan River M-55-76-3

Unlike the federal GNIS-ID, the Kittle Number includes information about upstream/downstream relationships. With the Mississippi as the primary flowpath, the Minnesota, Blue Earth, and Watonwan Rivers each represent another level of tributary above the Mississippi, and are each represented by another tributary-level digit in the Kittle system.


What constitutes compliance?

Minnesota state agencies must be capable of translating their river codes into a form consistent with this standard for the purposes of exchanging data among other state agencies and local governments. Agencies may store and administer alternative river codes as long as the capability exists to readily convert them. Agencies may also distribute or publish alternative river codes as long as the standard codes are available as an option. Because the reach is often a segment of a full river or watercourse, it will not be possible to translate from a watercourse (full river) level to a reach (river segment) level. Some data are only meaningful at the watercourse level. It is always possible, however, to aggregate multiple reaches (river segments) back to a watercourse (full river) - since a watercourse is made up of one or more reaches. Therefore it is recommended that state agencies integrate the reach portion of the standard into new system designs, and where possible when redeveloping existing systems.

How will compliance be measured?

No direct monitoring of compliance will be conducted. Evidence of compliance will be based on reports of satisfactory data transfers among state agencies, federal and local agencies, the private sector and citizen customers; and the development of distribution strategies that incorporate the standard codes. Further evidence of compliance will be the frequency of use of the NHD rivers linework and the proliferation of applications able to use river-related data across agency and program lines because the data have been indexed in accordance with this standard.

Related Information:

Further information about this standard may be obtained from the Minnesota Geospatial Information Office (MnGeo); 300 Centennial Building; 658 Cedar Street; St. Paul, MN 55155; phone: 651-201-2499;

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