Research Areas > Data Management > National Hydrography Dataset

Project: National Hydrography Dataset (NHD) Stewardship

Background and Objectives

The National Hydrography Dataset is a consistent, seamless, and comprehensive GIS database that displays hydrographic features throughout the country. The USGS created the dataset by digitizing hydrologic features from topographic maps, and then supplemented this basic layer with additional information from other sources. The NHD is dynamic and intended to be continuously improved via the addition of new or modified water features. As updates are made, they simultaneously become available to the public for download.

At the most basic level, the NHD is a map of all water features in the US and the structures that are associated with them. However, the map of the Santa Ana River watershed shown below suggests the inherent complexity of maintaining and correcting NHD data. Here you see the watershed boundary for the Santa Ana River sub-basin. Rivers, streams and other linear water features are symbolized as “flowline” and “line” features. Water bodies are “polygon” features that can include lakes, ponds, reservoirs, wide river beds, and inundated areas. Finally, the NHD also contains “point” features representing things such as stream gauges, wells, and intake and outflow pipes.

All of these features are included in a network that indicates both the connections between different features, and the path of water flow. On the close-up of the Newport Beach area shown below, the black arrows indicate the direction of flow along each reach or stream segment, and the red dots show the location of each node or junction. This knowledge of the flow network is critical to the use of NHD for water resource management.

SCCWRP entered into an agreement to work with the US Geological Survey (USGS) as a local steward of the NHD. SCCWRP initially agreed to edit portions of the Santa Ana sub-basin, with potential to expand to the San Gabriel and Los Angeles watersheds in the future.

Status

This project was initiated in 2008 and completed in 2011.

Methods

Under the guidance of the principal NHD steward for California, local stewards like SCCWRP were chosen based on their familiarity with sub-basin or watershed level hydrography. Local stewards were then trained to use specialized NHD editing tools and submit changes directly to USGS. SCCWRP developed contacts with people and agencies knowledgeable about changes in local water resources to be incorporated into the NHD. SCCWRP also established a system for collecting updates and ensuring that they were valid. Once updates were received, the corrections were made and the downloadable databases were updated.

Findings

SCCWRP submitted over 1,200 corrections of river and stream flowlines, waterbodies, and associated hydrologic features in the Santa Ana River watershed to the NHD Stewardship Program in February 2011. These corrections were based on input from member agencies, SCCWRP staff, and other stakeholders, and were verified using current high resolution imagery and other reliable sources. Future collaborations with the USGS may involve continuing and/or expanding SCCWRP's NHD stewardship role in the southern California region.

Partners

The main collaborator on this project was the USGS.

Poster

B Schaffner. January 2009. The Role of SCCWRP as a Steward of the National Hydrography Dataset for the Santa Ana River Watershed. Presented at 2nd Annual SCCWRP Symposium.