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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 National Hydrography Support.

Tools for National Hydrography Datasets

Page NavigationMarkup Application | Hydrographic Addressing (HydroAdd and HEM) | NHD Utilities | NHD GeoConflation Tool | NHD Update Tool | Geographic Names Information System (GNIS) | Compare Tool | NHD Watershed Tool 

Markup Application

As of December 1, 2022, the Markup App is no longer accepting incoming markups. You can still log in to review your markup history, browse the map, or identify features, but cannot submit markups.

► For more information, please email

The Markup Application is a web-based mapping communication tool that allows users to suggest edits, or “markups”, to the National Hydrography Dataset (NHD) and Watershed Boundary Dataset (WBD). Approved markups also propagate from the NHD and WBD to derived NHDPlus High Resolution (NHDPlus HR) data products. 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 is designed to work in the Google Chrome and Microsoft Edge Chromium web browsers.

All markups are reviewed and validated by approved USGS editors and State stewards before they are implemented in the NHD or WBD. Markup review and status changes are handled through the Markup Reviewer tool, which is an ArcGIS Desktop Add-In tool available only to USGS and Stewards.

  • 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) website. For access, please email
  • The training video for the Markup Application is available from the USGS website or USGS YouTube Channel. The lesson covers how to access and navigate the Markup Application, add and navigate reference layers, and understand the life cycle of markups.
  • Markup App Help Documentation.

Hydrographic Addressing

►Contact: To learn more about HydroAdd, contact | To learn more about HEM contact

Hydrographic addressing, also referred to as linear referencing, indexing, or linking, is a means to align data features relevant to the stream network to be coincident with National Hydrography Dataset (NHD) features. Addressing data to the NHD enables it to be used as a base for analysis and knowledge. Any kind of hydro-related observations can be addressed to the NHD such as observations relating to hydrology, geomorphology, water quality, biology, regulations, etc.

Hydrography Addressing (HydroAdd) Tool

The Hydrography Addressing Tool, or HydroAdd, is a web-based tool that allows users to address data to the National Hydrography Dataset (NHD). The addressing process also spatially joins some NHD flowline attributes to data features being addressed. Because HydroAdd is a web-based tool, multiple users can collaborate on shared projects.

To use HydroAdd you must have an active Esri ArcGIS Online account.

Hydrography Event Management (HEM) Tool

The Hydrography Event Management (HEM) Tool is a desktop addressing tool for use in Esri ArcMap. The HEM tool can create point, line, and polygon events. 

To use HEM tools, you must have ArcMap 10.7.1.

Download: HEM Tool for ArcGIS 10.7.1

NHD Utilities

►Contact: For more information, email National Hydrography Support.

Note: Versions prior to the posted version are unsupported. If users need previous versions of the NHD Utilities contact National Hydrography Support.

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 Utilities for ArcGIS 10.7.1

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.

NHD GeoConflation Tool

Contact: For more information about NHD GeoConflation, contact NHD GeoConflation Tool (GCT) Support or contact the National NHD POC at National Hydrography Support.

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 containing 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.

NHD Update Tool

Contact: For more information or training, email National Hydrography Support .

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.

Geographic Names Information System (GNIS)

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

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.

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.

*Disclaimers: Non-endorsement of Commercial and Other Non-USGS Products and Services | USGS Public-Domain Software