Office of Water Prediction Data Services

National Water Prediction Service (NWPS) APIs

This page lists the currently available NWPS data services and links to these services.

NWPS Application API

The NWPS API makes available the data used by the NWPS application, which includes official NWS streamflow forecasts, stream observations, National Water Model streamflow output, crest history, flood impacts, low water history, flood category levels, and location metadata. This service does not contain historical data other than crest and low water history.

NWPS Hydrologic Ensemble Forecast Service (HEFS) API (Experimental)

Note: This API is not supported 24/7 and may be modified without advance notice.

The experimental NWPS HEFS Forecast API can be used to retrieve real-time and historical HEFS forecast data for NWPS locations. The API provides complete ensembles, ensemble time-step quantiles, and quantiles based on each ensemble member's maximum value within various time frames. The HEFS is a service developed by the National Weather Service (NWS) to provide ensemble streamflow predictions. HEFS has been implemented at NWS River Forecast Centers (RFCs) for over 3,000 locations throughout the United States. HEFS integrates meteorological forecasts with hydrologic modeling to produce probabilistic streamflow forecasts and other hydrological variables. The service assesses the potential impacts of high-flow events and assesses flood risk. The service currently serves 10 days of data. Guidance from individual RFCs may not be available at all times.

NWPS National Water Model (NWM) API (Experimental)

Note: This API is not supported 24/7 and may be modified without advance notice.

The experimental NWPS National Water Model (NWM) API can be used to retrieve NWM output for 3.2 million stream reaches. The NWM is a hydrologic modeling framework that simulates the water cycle to generate near real-time analyses and forecast guidance. The NWM complements the official streamflow forecasts issued by the National Weather Service's 13 River Forecast Centers by providing guidance for stream reaches, most of which are ungauged, across the continental United States (CONUS), South-Central Alaska (Cook Inlet, Copper River Basin, and Prince William Sound regions), Hawaii, Puerto Rico, and the U.S. Virgin Islands. The NWM also generates total water level (TWL) guidance along the coastlines of these same regions, excluding Alaska. The NWM provides hydrologic guidance and is not an official forecast product.

The NWPS NWM API currently provides access to the most recent streamflow model run as well as a three-day rolling archive of past model runs for the following configurations: short_range, medium_range, medium_range_blend, analysis_assim, and analysis_assim_extend. It serves one day for the long_range configuration. The API additionally serves three days of total water level model runs for the following configurations: short_range, medium_range, medium_range_blend, analysis_assim, analysis_assim_extend, short_range_psurge, medium_range_psurge, medium_range_blend_psurge (psurge data is only available during hurricanes).