This data release provides the reanalysis streamflow data from versions 1.2, 2.0, and 2.1 of the National Water Model structured for timeseries extraction. The impact of this is that user can query time series for a given NHDPlusV2 COMID without downloading the hourly CONUS files and extracting the sample of relevant values.

The data is hosted on the RENCI THREDDS Data Server and is accessible via OPeNDAP at the follwoing URLs:

Version 1.2
(https://thredds.hydroshare.org/thredds/catalog/nwm/retrospective/catalog.html?dataset=NWM_Retrospective/nwm_retro_full.ncml)
- Spans 1993-01-01 00:00:00 to 2017-12-31 23:00:00
- Contains 219,144 hourly time steps for
- 2,729,077 NHD reaches

Version 2.0
(https://thredds.hydroshare.org/thredds/catalog/nwm/retrospective/catalog.html?dataset=NWM_Retrospective/nwm_v2_retro_full.ncml)
- Spans 1993-01-01 00:00:00 to 2018-12-31 00:00:00
- Contains 227,903 hourly time steps for
- 2,729,076 NHD reaches

Version 2.1
(https://cida.usgs.gov/thredds/catalog/demo/morethredds/nwm/nwm_v21_retro_full.ncml)
- Spans 1979-02-02 18:00:00 to 2020-12-31 00:00:00
- Contains 227,903 hourly time steps for
- 2,729,076 NHD reaches

Raw Data
(https://registry.opendata.aws/nwm-archive/)
- 227,000+ hourly netCDF files (depending on version)

## DDS

The data description structure (DDS) can be viewed at the NcML page for each respective resource (linked above). More broadly each resource includes:

- A _1D_ time array - **hours** since 1970-01-01 00:00
- A _1D_ latitude array - **coordinate** (Y) information
- A _1D_ longitude array - **coordinate** (X) information WGS84
- A _1D_ feature_id array - **NHDPlus V2 COMID** (NWM forecast ID)
- A _2D_ streamflow array - **Q (cms)** [feature_id, time]

## R package

The `nwmTools` R package provides easier interaction with the OPeNDAP resources. Package documentation can be found [here](https://mikejohnson51.github.io/nwmTools/) and the GitHub repository [here](https://github.com/mikejohnson51/nwmTools).

# Collaborators:

[Mike Johnson](https://mikejohnson51.github.io/), [David Blodgett](https://www.usgs.gov/staff-profiles/david-l-blodgett?qt-staff_profile_science_products=3#qt-staff_profile_science_products)

# Support:

This effort is supported by the Consortium of Universities for the Advancement of Hydrologic Science, Inc. under the HydroInformatics Fellowship. See program [here](https://www.cuahsi.org/data-models/hydroinformatics-innovation-fellowship/)

# Publications

J.M. Johnson, David L. Blodgett, Keith C. Clarke, Jon Pollack. (2020). "Restructuring and serving web-accessible streamflow data from the NOAA National Water Model historic simulations". _Nature Scienfic Data_. (**In Review**)