# Water Data APIs > Documentation and machine-readable indexes for the USGS water data APIs, which publish streamflow, groundwater, water-quality, and imagery observations for the United States. Every link below is a document this site publishes or an API this site documents. Documentation pages also exist as plain markdown at the same URL with "index.html.md" appended, and those are the URLs listed here where they exist. Retrieve data from the endpoints under "API endpoints" rather than by fetching these pages. Requests are rate limited; register a free API key on the signup page and send it as the api_key query parameter or the X-Api-Key request header. ## Start here - [USGS Water Data APIs](https://api.waterdata.usgs.gov/): Discover modernized USGS water data APIs for streamflow, daily values, monitoring locations, water quality, and imagery. - [Agent and Automation Integration Guide](https://api.waterdata.usgs.gov/docs/agents/index.html.md): Machine-readable entry points for automated consumers of this site: the llms.txt index, Markdown page copies, the... - [Get a USGS Water Data API Key](https://api.waterdata.usgs.gov/signup/): Register a free API key for the USGS water data APIs to receive higher rate limits and make more requests per hour. ## Documentation - [USGS Water Data API Documentation](https://api.waterdata.usgs.gov/docs/): Browse documentation for every API hosted on api.waterdata.usgs.gov, including the OGC, STAC, samples, and imagery... - [Getting Started with the NIMS Imagery API](https://api.waterdata.usgs.gov/docs/nims/index.html.md): Learn how the NIMS API lists cameras at USGS gaging stations and how to build full image URLs from the filenames it... - [HIVIS Imagery Visualization Application](https://api.waterdata.usgs.gov/docs/nims/hivis/index.html.md): HIVIS is the web application for browsing images and time-lapse videos that NIMS collects at USGS monitoring sites. - [About the National Imagery Management System](https://api.waterdata.usgs.gov/docs/nims/overview/index.html.md): NIMS is the serverless USGS infrastructure that collects, stores, processes, and delivers imagery from monitoring... - [Getting Started with USGS Water Data OGC APIs](https://api.waterdata.usgs.gov/docs/ogcapi/index.html.md): Learn how the USGS OGC API endpoints are structured and how to query continuous values, daily values, and location... - [Complex Water Data Queries with CQL2](https://api.waterdata.usgs.gov/docs/ogcapi/complex-queries/index.html.md): Use CQL2 POST requests to query the USGS water data APIs for multiple sites, parameter codes, or value ranges at once. - [Making Efficient Water Data API Queries](https://api.waterdata.usgs.gov/docs/ogcapi/efficiency/index.html.md): Speed up USGS water data API requests by limiting fields, narrowing time ranges, and splitting large queries into... - [Access USGS Water Data with QGIS](https://api.waterdata.usgs.gov/docs/ogcapi/gis/index.html.md): Follow a step-by-step walkthrough for adding USGS water data OGC API layers to a QGIS project and styling the results. - [Using API Keys with USGS Water Data APIs](https://api.waterdata.usgs.gov/docs/ogcapi/keys/index.html.md): Pass an API key through the api_key query parameter or the X-Api-Key header to raise your USGS water data rate limits. - [USGS OGC API Usage Metrics](https://api.waterdata.usgs.gov/docs/ogcapi/metrics/): Review a daily updated chart of request volume against the USGS water data OGC API endpoints over the past month. - [Migrating to Modernized USGS Water APIs](https://api.waterdata.usgs.gov/docs/ogcapi/migration/index.html.md): Map your waterservices.usgs.gov queries onto the equivalent api.waterdata.usgs.gov OGC API endpoints and response... - [USGS Water Data API Versioning Policy](https://api.waterdata.usgs.gov/docs/ogcapi/versioning/index.html.md): Understand how the USGS water data OGC APIs are versioned and which changes the project treats as breaking changes. - [Getting Started with the USGS Water Data STAC API](https://api.waterdata.usgs.gov/docs/stac/index.html.md): Learn how the USGS Water Data STAC API organizes catalogs, collections, and items, and how to query them for data files. ## API endpoints - [Continuous Values](https://api.waterdata.usgs.gov/ogcapi/v0/collections/continuous): This API provides the most recent real-time measurements of streamflow, gage height, and hundreds of other... - [Daily Values](https://api.waterdata.usgs.gov/ogcapi/v0/collections/daily): Interested in historical summarized daily data about our nation's streams, lakes and wells? This API provides a... - [Monitoring Locations](https://api.waterdata.usgs.gov/ogcapi/v0/collections/monitoring-locations): Location information is basic information about the monitoring location including the name, identifier, agency... - [Time Series Metadata](https://api.waterdata.usgs.gov/ogcapi/v0/collections/time-series-metadata): Daily data and continuous measurements are grouped into time series, which represent a collection of observations of... - [OGC-Compliant APIs](https://api.waterdata.usgs.gov/docs/ogcapi/): USGS offers Open Geospatial Consortium (OGC) compliant APIs, which will let you download continuous service... - [Water Quality Services](https://api.waterdata.usgs.gov/samples-data/docs): The USGS and the U.S. Environmental Protection Agency (EPA) each collect vast amounts of water quality data. The... - [USGS Water Data Statistics](https://api.waterdata.usgs.gov/statistics/v0/docs): This service provides endpoints for access to computations on the historical record regarding water conditions. - [Real-Time Flood Impacts](https://api.waterdata.usgs.gov/rtfi-api/docs): The Real-Time Flood Impact (RTFI) API exposes the locations, called Flood Impact Locations, where the USGS measured... - [National Imagery Management System](https://api.waterdata.usgs.gov/docs/nims): The National Imagery Management System (NIMS) collects, stores, processes, and delivers imagery from USGS gaging... ## Machine-readable indexes - [API index (apis.json)](https://api.waterdata.usgs.gov/apis.json): JSON index of every documented USGS water data API, carrying names, descriptions, and links. - [Sitemap (sitemap.xml)](https://api.waterdata.usgs.gov/sitemap.xml): XML sitemap listing the canonical URL of every page this site publishes. ## Optional - [USGS Water Quality API](https://api.waterdata.usgs.gov/samples-data/docs): The USGS Samples API provides access to USGS water quality information. - [Water Quality Portal APIs](https://www.waterqualitydata.us/beta/webservices_documentation/): The Water Quality Portal API provides access to publicly available discrete water-quality data from the USGS, EPA... (external resource served by www.waterqualitydata.us) - [Legacy Water Services](https://waterservices.usgs.gov/docs/): The original Water Services provides production-ready API access to USGS water data. (external resource served by waterservices.usgs.gov) - [Swagger UI Documentation](https://api.waterdata.usgs.gov/nims/v0/docs): The NIMS SwaggerUI provides an interactive OpenAPI reference for the National Imagery Management System endpoints... - [SwaggerUI Documentation](https://api.waterdata.usgs.gov/ogcapi/v0/openapi): The OGC API SwaggerUI provides an interactive OpenAPI reference for the USGS water data OGC API endpoints, query... - [Download USGS Water Data](https://api.waterdata.usgs.gov/download/): Use an interactive form to query the USGS Water Data OGC API and download the results as CSV files in a ZIP archive. - [STAC Explorer](https://api.waterdata.usgs.gov/stac-explorer/): Browse the collections and items published by the USGS Water Data STAC API and follow links to the underlying data...