# U.S. Geological Survey Hydrologic Unit Codes API

**Canonical:** https://apis.io/apis/u-s-geological-survey/u-s-geological-survey-hydrologic-unit-codes-api/  
**Provider:** U.S. Geological Survey — https://apis.io/providers/u-s-geological-survey/  
**Base URL:** https://earthquake.usgs.gov/fdsnws/event/1  
**Documentation:** https://www.usgs.gov/tools/asset-identifier-service-ais

U.S. Geological Survey Hydrologic Unit Codes API is one of 47 APIs that [U.S. Geological Survey](https://apis.io/providers/u-s-geological-survey/) publishes on the [APIs.io](https://apis.io/) network, described by a machine-readable OpenAPI specification. This API exposes 3 JSON Schema definitions. Tagged areas include hydrologic-unit-codes. The published artifact set on APIs.io includes an OpenAPI specification, API documentation, a getting-started guide, a JSON-LD context, authentication docs, and 3 JSON Schemas.

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 <https://water.usgs.gov/GIS/huc.html>.

## Operations (8)

| Method | Path | Summary |
|---|---|---|
| GET | `/collections/hydrologic-unit-codes` | Get Hydrologic unit codes (HUCs) metadata |
| GET | `/collections/hydrologic-unit-codes/items` | Get Hydrologic unit codes (HUCs) items |
| OPTIONS | `/collections/hydrologic-unit-codes/items` | Options for Hydrologic unit codes (HUCs) items |
| POST | `/collections/hydrologic-unit-codes/items` | Get Hydrologic unit codes (HUCs) items with CQL2 |
| GET | `/collections/hydrologic-unit-codes/items/{featureId}` | Get Hydrologic unit codes (HUCs) item by id |
| OPTIONS | `/collections/hydrologic-unit-codes/items/{featureId}` | Options for Hydrologic unit codes (HUCs) item by id |
| GET | `/collections/hydrologic-unit-codes/queryables` | Get Hydrologic unit codes (HUCs) queryables |
| GET | `/collections/hydrologic-unit-codes/schema` | Get Hydrologic unit codes (HUCs) schema |

## Machine-readable artifacts (13)

- **OpenAPI** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/openapi/u-s-geological-survey-hydrologic-unit-codes-api-openapi.yml
- **Conformance** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/conformance/u-s-geological-survey-conformance.yml
- **Documentation** — https://earthquake.usgs.gov/fdsnws/event/1/
- **GettingStarted** — https://earthquake.usgs.gov/earthquakes/feed/
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/json-schema/usgs-earthquake-api-earthquake-properties-schema.json
- **JSONLD** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/json-ld/usgs-earthquake-api-context.jsonld
- **Examples** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/examples/usgs-earthquake-api-earthquake-properties-example.json
- **Documentation** — https://api.waterdata.usgs.gov/docs/
- **Authentication** — https://api.waterdata.usgs.gov/signup/
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/json-schema/usgs-water-data-api-monitoring-location-properties-schema.json
- **JSONSchema** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/json-schema/usgs-water-data-api-time-series-properties-schema.json
- **JSONLD** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/json-ld/usgs-water-data-api-context.jsonld
- **Examples** — https://raw.githubusercontent.com/api-evangelist/u-s-geological-survey/refs/heads/main/examples/usgs-water-data-api-monitoring-location-properties-example.json

## Other U.S. Geological Survey APIs (12)

- [USGS Water Data APIs](https://apis.io/apis/u-s-geological-survey/water-data-ogc-api/)
- [Asset Identifier Service (AIS)](https://apis.io/apis/u-s-geological-survey/asset-identifier-service-ais/)
- [Seismic Design Web Service](https://apis.io/apis/u-s-geological-survey/seismic-design-web-service/)
- [ScienceBase](https://apis.io/apis/u-s-geological-survey/sciencebase/)
- [StreamStats Web Services](https://apis.io/apis/u-s-geological-survey/streamstats-web-services/)
- [USGS Water Services (Legacy)](https://apis.io/apis/u-s-geological-survey/usgs-water-services/)
- [U.S. Geological Survey Catalog API](https://apis.io/apis/u-s-geological-survey/u-s-geological-survey-catalog-api/)
- [U.S. Geological Survey Earthquakes API](https://apis.io/apis/u-s-geological-survey/u-s-geological-survey-earthquakes-api/)
- [U.S. Geological Survey Monitoring Locations API](https://apis.io/apis/u-s-geological-survey/u-s-geological-survey-monitoring-locations-api/)
- [U.S. Geological Survey Reference Data API](https://apis.io/apis/u-s-geological-survey/u-s-geological-survey-reference-data-api/)
- [U.S. Geological Survey Time Series Data API](https://apis.io/apis/u-s-geological-survey/u-s-geological-survey-time-series-data-api/)
- [U.S. Geological Survey Agency Codes API](https://apis.io/apis/u-s-geological-survey/u-s-geological-survey-agency-codes-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/u-s-geological-survey/u-s-geological-survey-hydrologic-unit-codes-api/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/u-s-geological-survey/.