# USGS Water Services hydrologic-unit-codes API

**Canonical:** https://apis.io/apis/usgs-water/usgs-water-hydrologic-unit-codes-api/  
**Provider:** USGS Water Services — https://apis.io/providers/usgs-water/  
**Base URL:** https://waterservices.usgs.gov/nwis/iv/  
**Documentation:** https://waterservices.usgs.gov/docs/instantaneous-values/instantaneous-values-details/

USGS Water Services hydrologic-unit-codes API is one of 43 APIs that [USGS Water Services](https://apis.io/providers/usgs-water/) 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/usgs-water/refs/heads/main/openapi/usgs-water-hydrologic-unit-codes-api-openapi.yml
- **Documentation** — https://api.waterdata.usgs.gov/docs/
- **Website** — https://api.waterdata.usgs.gov/

## Other USGS Water Services APIs (12)

- [USGS Instantaneous Values Service](https://apis.io/apis/usgs-water/instantaneous-values/)
- [USGS Daily Values Service](https://apis.io/apis/usgs-water/daily-values/)
- [USGS Site Service](https://apis.io/apis/usgs-water/site-service/)
- [USGS Statistics Service](https://apis.io/apis/usgs-water/statistics-service/)
- [USGS Groundwater Levels Service](https://apis.io/apis/usgs-water/groundwater-levels/)
- [Water Quality Portal (WQP) API](https://apis.io/apis/usgs-water/water-quality-portal/)
- [USGS Water Data Statistics API](https://apis.io/apis/usgs-water/statistics-next-gen/)
- [USGS Water Services agency-codes API](https://apis.io/apis/usgs-water/usgs-water-agency-codes-api/)
- [USGS Water Services altitude-datums API](https://apis.io/apis/usgs-water/usgs-water-altitude-datums-api/)
- [USGS Water Services aquifer-codes API](https://apis.io/apis/usgs-water/usgs-water-aquifer-codes-api/)
- [USGS Water Services aquifer-types API](https://apis.io/apis/usgs-water/usgs-water-aquifer-types-api/)
- [USGS Water Services channel-measurements API](https://apis.io/apis/usgs-water/usgs-water-channel-measurements-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/usgs-water/usgs-water-hydrologic-unit-codes-api/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/usgs-water/.