National Hydrography


The following tools are provided to assist in the use of NHD data. Any problems encountered when using these tools should be reported to

Tools included below:

No special tool is needed to display or work with the NHD other than a Geographic Information System (GIS). The NHD is a geospatial dataset. Some features of the NHD, such as geometric navigation, only work within the Esri software. An alternative to working with a GIS is to display the NHD in The National Map Viewer on the Web. To do this, click on Get Data > Go to the NHD Viewer.

Markup Application

The Markup Application is a web-based mapping communication tool that allows users to suggest edits, or “markups”, to the NHD, WBD, and NHDPlus HR. Anyone can suggest corrections and improvements to the data. A Gmail, ArcGIS Online, or Microsoft Office account is needed to authenticate into the web application. The application has been designed to work in the Google Chrome Web Browser only.

Suggested edits will be reviewed by the USGS and the NHD state stewards before they are approved for incorporation into the NHD or WBD datasets and future NHDPlus HR Refresh products. Markup review and status changes will be handled through the Markup Reviewer tool - ArcGIS Add-in tool available to NHD and WBD stewards and editors.

  • Access the Markup App.
  • Access the Markup Reviewer Tool: The Markup Reviewer, used by the USGS and the NHD state stewards to review suggested edits, is available for download at the USGS Hydrographic Data Community (HDC). For access to the HDC site, please contact Lily Niknami (
  • The training video for the Markup Application is available on this USGS site or Youtube. The lesson covers how to access and navigate the Markup Application, create and delete your markups, add and navigate reference layers, and understand the life cycle of markups.
  • Markup App Help Documentation and Frequently Asked Questions
  • For more information about the Markup App or Markup Reviewer, or to request training, please contact

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NHD GeoConflation Tool

The NHD GeoConflation tool is used to migrate (conflate) reachcodes and permanent identifiers plus other attribute information from a SOURCE database to a larger-resolution TARGET database. The purpose behind the tool is to maintain the allocated reachcodes contained in SOURCE data as much as possible due to linkages from other datasets such as NHD Event features. For more information on this tool click on the above link or contact

The GeoConflation Tool is one of several possible methods available to update the National Hydrography Dataset (NHD). The tool was originally developed to automate the “NHD Create Process” used to generate the high-resolution (1:24,000-scale) NHD data from the medium-resolution (1:100,000-scale) data. NHD GeoConflation is the combination of components from two databases into a single database. The basic goal of conflation is to conserve reach codes and unique identifiers from the USGS NHD Production data. The original attribution (or SOURCE) is transferred to the new geometry contained in a TARGET dataset by means of spatial location. So far that is normal conflation as far as GIS systems are concerned, but the tool also enforces the business rules of the NHD model and creates a history of the reach code transfers via the reach cross reference table. This is why it is referred to as GeoConflation.

One way to think of the process is "change detection and displacement.” Two datasets are used by the tool: the SOURCE which contains the current production geometry and attribution, and a new database of geometry with minimal attribution, called the TARGET. The SOURCE data is then spatially compared to the TARGET data. Where the geometries of flow lines (streams, rivers, canals, etc.) and water bodies (lakes, reservoirs, estuaries) match within specified tolerances, then attribution is automatically transferred. Close matches are flagged for review by the editor to determine if there is an actual match or not. If the feature exists in the original, but not in the target, the original feature is marked as a “missed feature,” which would ultimately lead to the feature being removed from the production data. In the alternative circumstance where the feature exists in the target but not the source, a new ReachCode is applied to the feature and a “create new feature” is automatically generated.

As in any update process the results of the output are only as good as the input. So a majority of the work is actually done during the preparation of the TARGET dataset. The updated geometry, TARGET data, must have feature types/codes, connectivity and flow direction for flow lines, and be in the correct NHD schema in order to be used in the GeoConflation process. The end result of the process is a dataset consisting of the new geometry complete with reach codes and unique identifiers where needed. All changes to the original data will have been tracked within the model schema. In addition, the target data must pass required QA/QC checks before the final data is integrated into the NHD production database.

For more information about NHD GeoConflation, contact Partner Support through or contact your regional Partner Support Point of Contact.

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Hydrography Event Management (HEM) Tool

HEM Point of Contact: Michael Tinker, For general information, contact us at

The Hydrography Event Management (HEM) Tools are a set of shared components to allow for creation, management, and refresh of event data that is referenced to hydrography data in the NHDinGeo format. Events are informational data that are linked to the NHD using a linear referencing system on NHDFlowlines. The use of events is a key characteristic of the NHD by allowing vast amounts of scientific information to be linked to the NHD while keeping the design simple and by making advanced analysis techniques possible. The HEM tool handles all the linear referencing mechanics to make working with events easy. It works on point, line, and area events and allows events to be located interactively, imported, or calculated.

Please visit the Hydrologic Event Management webpage for more information.

Download HEM


HEM Help and Documentation

Importing and Synchronizing Area Events

  • Synchronizing with HEM tool
  • Batch Synchronizing Point Events
  • HEM Area Import and QC
  • Training data: NHD131687.7z

For help, please contact

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NHD Metadata Viewer Tool

The Metadata Viewer Add-In tool for ArcMap 10.x allows for quick display of feature-level metadata and source citation records for NHD and WBD features. The tool also provides export options in PDF and Excel formats. Currently this tool operates with NHD model 2.2 data, on both NHD data downloads from the NHD FTP site, as well as on data acquired from the NHD stewardship site.The Metadata Viewer does not display dataset-level FGDC metadata, however, this is normally viewed in ArcCatalog.

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NHD Utilities

The NHD Utilities is a suite of stand-alone software functions that were designed to help users manipulate National Hydrography Dataset (NHD) data. These tools are not necessarily part of the maintenance/update process for NHD, but are very useful to those performing different sorts of data manipulation and analysis with NHD data. This suite of tools includes; Network Builder, Build Flow, M-Value Utility, Geodatabase to Shapefile (GDB2Shp), Shapefile to Geodatabase (Shp2GDB), Subset by Polygon, and NHD Merge. The USGS NGTOC maintains on one version of these NHD Utilities usually for the current version of the ESRI ArcGIS application.

ArcGIS 10.5.1: NHD Utilities v3.4.2.0

Versions prior to the posted version are unsupported. If users need previous versions of the NHD Utilities contact

What's included:

  • NHD Network Builder: The NHD uses a utility geometric network within the ESRI geodatabase. This network allows the user to use ESRI’s Utility Network Analyst extension to perform certain analysis techniques. This network must be deleted when performing edits or re-projecting the NHDFlowline feature class. After re-projecting or altering NHDFlowline data, it is necessary to re-build the geometric network to restore flow and directionality to work with Utility Network Analyst. Network Builder is a tool that rebuilds the geometric network, creates and sets the “Enabled” field, and sets the flow direction within the context of the “FlowDir” attribute. The tool does not rebuild or update the NHD Flow table.
  • NHD Build Flow: The NHD Build Flow utility requires the input of an NHD subbasin file geodatabase. The tool builds a geometric network using the NHDFlowline feature class within the geodatabase. Each node within the geometric network represents a confluence of two or more NHDFlowline features. This utility uses these nodes to populate the NHDFlow table with in and out flow directions for each node, based on the FlowDir attribute within the NHDFlowline feature class. The result is a populated NHDFlow table that shows the flow of water throughout the network.
  • M-Value Utilities: M-Values, or measures, are the percentage upstream from a given location based on the features reachcode on an NHDFlowline. Measures range from 0-100 percent with 0 being the most downstream point of a reach (mouth), and 100 being the most upstream end of the reach (source). This is opposite of the flow/digitized direction of the feature. The M-Value Utility assigns measures to reached flow lines only. Each reached feature will have measure associated with the reach code assigned to that feature. The M-Value provides the networked location of a point event or the extent of a linear event along a reach.
  • GDB2Shp: This utility will convert a NHD ESRI file geodatabase into a set of shapefiles and DBF tables which can then be used by other software. The output is stored under a specific folder directory specified by the user’s system environment variables. Please read the NHD Utilities User Guide in order to obtain more information.
  • Shp2GDB: This utility will convert a series of ESRI Shapefile and DBF tables that are stored in an NHD format to an ESRI file geodatabase. The input must be correctly formatted and located in the user’s system environment variables folder on order to be converted. Please read the NHD Utilities User Guide in order to obtain more information.
  • Subset by Polygon: The Subset by Polygon tool (ESRI Add-in) works within an ArcGIS session and is not a standalone executable. The tool allows users to create subsets of the NHD data based on one or more polygons from a CustomArea feature class within a NHD geodatabase. This tool only works on fully populated NHD data.
  • NHD Merge: The NHD Merge tool joins two or more NHD geodatabases into a single geodatabase.  For ease of use, it is recommended that the input geodatabases be in the same folder.

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Geographic Names Information System (GNIS)

Access GNIS to check, submit new, or make changes to names in GNIS. 

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NHD Watershed Tool

The NHD Watershed Tool Page was removed from public access for a while until we received feedback that, although some of it is dated in terms of tool usage, much of it is still very relevant in terms of processing steps. This page documents these steps as well as any other training documents available as of 2013. If you would like feedback on how any particular processing step may relate to more recent tools, please contact Pete Steeves,

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Compare Tool

The vector Compare Tool is designed for use with ArcMap 10.2.2 and is used to compare features/rows between two feature classes/tables in two geodatabases with the same schema and spatial reference. The geodatabases can be in either personal or file geodatabase format. The tool creates a new geodatabase that displays differences in geometry and attributes.


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National Hydrography Support

Support for NHD, WBD, & NHDPlus HR
National Geospatial Program (NGP)

USGS Markup Application (Markup App) Support Mailbox

Program Support
Phone: 888-275-8747

NHD GeoConflation Tool (GCT) Support Mailbox

Program Support
National Geospatial Program (NGP)
Phone: 907-786-7042

Hydrography Event Management Tool (HEM) Support Mailbox

Program Support
National Geospatial Program (NGP)
Phone: 888-275-8747