National Hydrography


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

The National Hydrography Dataset (NHD), Watershed Boundary Dataset (WBD), or NHDPlus High Resolution (NHDPlus HR) are geospatial datasets that can be accessed in The National Map Advanced Viewer or by using a Geographic Information System (GIS). Some features, such as geometric navigation, only work within Esri software packages.

Tools for National Hydrography Datasets:


Markup Application

Contact: For more information or to request training, email

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.

back to top


Hydrography Event Management (HEM) Tool

Contact: Michael Tinker, For general information, email

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 Tool for ArcGIS 10.7.1 

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

back to top


NHD Utilities

Contact: For more information, email

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.

Download: NHD Utilies for ArcGIS 10.7.1

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.

back to top


NHD GeoConflation Tool

Contact: For more information, email

The GeoConflation Tool is one of several tools available to NHD Editors to update the National Hydrography Dataset (NHD). Conflation aligns information from a source dataset to a target dataset. In the case of GeoConflation, the information is matched spatially such that the attribution from the source dataset is transferred to the new geometry contained in a target dataset by means of spatial location.

The NHD GeoConflation tool is used to conflate reachcodes, permanent identifiers, and other attribute information such as geographic names from the USGS NHD Production Database held at USGS to datasets contraining updated hydrography features. The purpose is to maintain allocated reachcodes contained in the NHD Production Data as much as possible to support linkages such as NHD Event features. 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.

In this process, the source dataset containing the current geometry and attribution and the target dataset with new geometries and  minimal attribution are spatially compared. Where the geometries (e.g. streams, rivers, lakes, etc.) match within specified tolerances, the attribution is automatically transferred. Close matches are flagged for review by the NHD 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 reviewed for removal from the NHD Production Database. 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 in the target dataset 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 the National NHD POC at

back to top


NHD Update Tool

Contact: For more information or training, email

The NHD Update Tool is a desktop application that allows users to get job requests from the Hydrography Maintenance Portal (HMP), edit data, preform quality control checks, and either send the job back to the USGS or submit as a problem job for review. The NHD Update Tool connects to USGS services to check Geographic Names Information System (GNIS), Reachcodes, and In/Out Flows between Hydrologic Units. The Update Tool also connects Workflow Manager and the NGTOC File Transfer Protocol site for tracking jobs and sending data to USGS. Finally, the NHD Update Tool Connects to online help documentation, which can be updated when changes are made to the NHD.  

NHD Update Tool can be used to perform a variety of edits to 

  • Complete Network Improvement 

  • Complete Image Integration 

  • Import International Data 

  • Resolve QC Errors and Upload Data from edits made by the GeoConflation Tool and Hydrography Event Management (HEM) Tool 

  • Review and Resolve Suggestions made in the MarkUp Application 

To use the NHD Update Tool potential users must attend the NHD Basics Class (2.5 hours) and the NHD Update Tool Training (8 hours), as well as completing several training jobs.

back to top


Geographic Names Information System (GNIS)

Access the Geographic Names Information System (GNIS) to check, submit new, or make changes to names in GNIS. 

back to top


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.


back to top


NHD Watershed Tool

Contact: For more information, including how processing steps relate to more recent tools, contact Pete Steeves,

The NHD Watershed Tool page documents processing steps as well as any other related training documents available as of 2013.

back to top


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