# Department of Interior hydrologic-unit-codes API

**Canonical:** https://apis.io/apis/doi/doi-hydrologic-unit-codes-api/  
**Provider:** Department of Interior — https://apis.io/providers/doi/  
**Base URL:** https://developer.nps.gov/api/v1  
**Documentation:** https://www.nps.gov/subjects/developer/index.htm

Department of Interior hydrologic-unit-codes API is one of 41 APIs that [Department of Interior](https://apis.io/providers/doi/) publishes on the [APIs.io](https://apis.io/) network, described by a machine-readable OpenAPI specification. Tagged areas include hydrologic-unit-codes. The published artifact set on APIs.io includes an OpenAPI specification and API documentation.

Hydrologic units are geographic areas representing part or all of a surface drainage basin or distinct hydrologic feature identified by a unique number (HUC), and a name. The United States is divided and sub-divided into successively smaller hydrologic units which are classified into four levels: regions, sub-regions, accounting units, and cataloging units. Each unit consists of two to eight digits based on the four levels of classification in the hydrologic unit system. Additional information can be found at &lthttps://water.usgs.gov/GIS/huc.html&gt.

## Machine-readable artifacts (3)

- **OpenAPI** — https://raw.githubusercontent.com/api-evangelist/doi/refs/heads/main/openapi/doi-hydrologic-unit-codes-api-openapi.yml
- **Documentation** — https://api.waterdata.usgs.gov/docs/
- **Migration** — https://api.waterdata.usgs.gov/docs/ogcapi/migration/

## Other Department of Interior APIs (12)

- [NPS Data API](https://apis.io/apis/doi/nps-data-api/)
- [USGS Earthquake Hazards Web Services](https://apis.io/apis/doi/usgs-earthquake-hazards-web-services/)
- [USGS Mineral Resources Data API](https://apis.io/apis/doi/usgs-mineral-resources-data-api/)
- [BLM GIS REST Services](https://apis.io/apis/doi/blm-gis-rest-services/)
- [USGS ScienceBase API](https://apis.io/apis/doi/usgs-sciencebase-api/)
- [Department of Interior agency-codes API](https://apis.io/apis/doi/doi-agency-codes-api/)
- [Department of Interior altitude-datums API](https://apis.io/apis/doi/doi-altitude-datums-api/)
- [Department of Interior aquifer-codes API](https://apis.io/apis/doi/doi-aquifer-codes-api/)
- [Department of Interior aquifer-types API](https://apis.io/apis/doi/doi-aquifer-types-api/)
- [Department of Interior channel-measurements API](https://apis.io/apis/doi/doi-channel-measurements-api/)
- [Department of Interior citations API](https://apis.io/apis/doi/doi-citations-api/)
- [Department of Interior combined-metadata API](https://apis.io/apis/doi/doi-combined-metadata-api/)

## Tags

hydrologic-unit-codes

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/apis/doi/doi-hydrologic-unit-codes-api/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/doi/.