# USGS Water Services aquifer-codes API

**Canonical:** https://apis.io/apis/usgs-water/usgs-water-aquifer-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 aquifer-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 aquifer-codes. The published artifact set on APIs.io includes an OpenAPI specification and API documentation.

Local aquifers in USGS data are identified by an aquifer name and geohydrologic unit code (a three-digit number related to the age of the formation, followed by a 4 or 5 character abbreviation for the geologic unit or aquifer name). For the age of formation (aquifer age), generally the smaller the number represents the younger the geohydrologic unit. Aquifer names and the definition of an aquifer can be very subjective. One rock unit may be called different aquifer names by different people. Local aquifers and layered aquifers are often grouped into larger named regional aquifers or aquifer systems. For example, the National Northern Atlantic Coastal Plain aquifer system (National aquifer) consists of five layered regional aquifers. Each regional aquifer is divided into two or more aquifers which may have a different name in each of the states in which the aquifer is found.

## Machine-readable artifacts (3)

- **OpenAPI** — https://raw.githubusercontent.com/api-evangelist/usgs-water/refs/heads/main/openapi/usgs-water-aquifer-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-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/)
- [USGS Water Services citations API](https://apis.io/apis/usgs-water/usgs-water-citations-api/)

## Tags

aquifer-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-aquifer-codes-api/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/usgs-water/.