Hydrographic and Impairment Statistics (HIS)

Canoeists explore Manzanita Lake in Lassen Volcanic National Park.
Canoeists explore Manzanita Lake in Lassen Volcanic National Park.

NPS photo / Mark McGowan

The Hydrographic and Impairment Statistics (HIS) database provides summary statistics of surface hydrography (acres of lakes, miles of streams, etc.) within and adjacent to each national park unit using the U.S. Geological Survey's (USGS) high resolution National Hydrography Dataset (NHD), the NPS Administrative Park Boundary Dataset, and other sources. Information regarding water impairments are supplied by state management agencies and attributed to NHD to derive impairment statistics for each national park unit. Impaired waters are identified by states according to the federal Clean Water Act (CWA) Sections 303(d) and 305(b). Using the functionality below you can obtain an estimate of the total miles of waterway (rivers, streams, canals, etc.), acreage of waterbodies (lakes, reservoirs, ocean, etc.), number of lakes, the acreage of icemass, and much more about any national park unit or summarized across the entire National Park System. You can also see which parks contain CWA impaired hydrography, which parks have no hydrography, and which parks are 'coastal'.

Search the HIS Database

View hydrographic and impairment statistics by park, region, network, or NPS Wild & Scenic River.
View statistics in descending order by selecting a hydrographic category.
View impairment statistics for different types of impairment.
View related reports.

Learn how statistics were created.

Methods - Summary of the methods used to generate hydrographic statistics
Caveats - Supplemental explanations of procedures used to generate hydrographic statistics
Standards - Basic introduction of water quality standards and Clean Water Act impairments

More Information
USGS National Hydrography Dataset
NPS Administrative Boundary Dataset
HIS Impairment Map Service
Clean Water Act
EPA Watershed Assessment, Tracking, and Environmental Results (WATERS)

Last updated: October 3, 2023