This data release consists of a sequence of high spatial resolution optical images used to derive remotely sensed estimates of surface flow velocity via particle image velocimetry (PIV). These data were acquired from the Salcha River in Alaska on August 31, 2018, along with field measurements of flow velocity used to assess the accuracy of image-derived velocity estimates. The images were obtained using a Hasselblad A6D-100C 100 megapixel digital mapping camera deployed within a pod mounted on the landing gear of a Robinson R44 helicopter. Image sequences were acquired at a frame rate of 1 per second (1 Hz) while the helicopter hovered in a fixed location approximately 200 m above the river. Also within the pod was an ATLANS GPS/Inertial Motion Unit (IMU) that recorded the position and orientation of the platform during the flight. This information was used to geo-reference the images by performing aerial triangulation and bundle adjustment within the SimActive Correlator3D software package. The bundle adjustment phase of this process also incorporated surveyed ground control targets that were placed in the field and were visible in the images. The resulting orthorectified images had a spatial resolution (pixel size) of 0.018 m and effectively stabilized the image sequence prior to PIV analysis. The images were converted to grayscale and saved as TIF files with corresponding world files (*.tfw) that contain the spatial referencing information for each image; the projected coordinate system is UTM Zone 6N, NAD83. The sequence consists of 68 individual images representing over one minute of data collection. The entire sequnce of TIF images and worldfiles is contained within a zip archive.

The U.S. Geological Survey collected field spectra collected from three rivers in Alaska September 19-21, 2016, to support research on remote sensing of river discharge. Reflectance measurements were made from bridges across the Chena River, Salcha River, and Montana Creek using an Analytical Spectral Devices FieldSpec3 spectroradiometer operated in reflectance mode. The original *.asd files are provided in this data release.

The U.S. Geological Survey in collaboration with the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL) collected topographic LiDAR surveys of four rivers in Alaska from August 8-9, 2017 to support research related to remote sensing of river discharge. Data were acquired for the Knik, Matanuska, Chena and Salcha Rivers using a Riegl VQ-580 LiDAR. The LiDAR was installed on a Robinson R44 Raven helicopter in a HeliPod that was designed and operated by CRREL. The LiDAR data included as part of this release include: a bare earth digital elevation model (DEM), an intensity or reflectence digital surface model (DSM) both in GeoTiff format, and compressed binary LAS files (LAZ) for each river surveyed.

Since 1993 the U.S. Geological Survey (USGS) has worked with the Alaska Department of Transportation and Public Facilities (ADOT&PF) to provide hydraulic assessments of scour for bridges throughout Alaska. As part of this effort, repeat channel cross section surveys, or channel soundings, have been collected at either the upstream or downstream side of bridges on an annual or as needed basis. Streambed and bank elevations are measured using USGS sounding weights and reels, weighted measuring tapes, acoustic Doppler current profilers, multibeam echo sounders and light detection and ranging and are referenced to the datum of as-built plan set to provide context for the streambed elevations in relation to bridge structures. Channel soundings are collected on an annual basis at most sites, however, as need soundings are collected due to flooding or periods of scour at select sites. Repeat channel soundings are used to access stream stability related to seasons, stage, and long-term aggradation or degradation as well as providing greater context for fixed mount streambed elevation monitoring. New measurements are appended to this data release after they have undergone formal QA/QC processing. Please note the updated date in the suggested citation.

Salinity levels in streams and tributaries of the Colorado River Basin have been a major concern for years. Recently, the United States Geological Survey’s (USGS) Next Generation Water Observing System (NGWOS) program expanded stream monitoring networks including the number of sites where continuous (15-minute) specific conductance is measured in the Colorado River Headwaters and Gunnison River subbasins located east of the Colorado-Utah state line (hereafter, UCOL). Salinity and total dissolved solids (TDS) can be estimated using specific conductance and water type as a proxy (McCleskey et al., 2023); thus, the UCOL is an ideal basin to apply the proxy. The data presented in this data release, including monitoring site information and water chemistry data, were used to develop a specific conductance and water type proxy model for salinity and TDS for sixty-six USGS monitoring sites in the UCOL. The monitoring site information and water-quality data for the sample sites in the UCOL were retrieved from the Water Quality Portal (Read et al., 2017) using the USGS dataRetrieval R package (De Cicco et al., 2018). The dataset contains 80,206 discrete water analyses collected between 1990 and 2023. The water chemistry data includes the concentrations of calcium, magnesium, sodium, potassium, chloride, sulfate, fluoride, nitrate, iron, boron, aluminum, alkalinity, and silica. A subset of this data includes 4,588 samples all of which have at least the concentrations of calcium, magnesium, sodium, potassium, chloride, and sulfate reported, a charge balance < ±10%, and a specific conductance imbalance < ±15%, unless the specific conductance was less than 100 µS/cm in which case the specific conductance difference was < ± 10 µS/cm. Finally, salinity and TDS were calculated for the discrete samples in the subset (McCleskey et al., 2023). References De Cicco, L.A., Hirsch, R.M., Lorenz, D. and Watkins, W.D., 2018. dataRetrieval: R packages for discovering and retrieving water data available from Federal hydrologic web services, doi:10.5066/P9X4L3GE. McCleskey, R.B., Cravotta, C.A., Miller, M.P., Tillman, F.D., Stackelberg, P., Knierim, K.J. and Wise, D., 2023. Salinity and total dissolved solids measurements for natural waters: An overview and a new salinity method based on specific conductance and water type. Applied Geochemistry, 154. Read, E.K., Carr, L., De Cicco, L., Dugan, H.A., Hanson, P.C., Hart, J.A., Kreft, J., Read, J.S. and Winslow, L.A., 2017. Water quality data for national-scale aquatic research: The Water Quality Portal. Water Resources Research, 53(2): 1735-1745

A height-above-river raster produced from 2008 lidar bare-earth elevations for the lower 10 kilometers of the Snow River flood plain is used as part of a geomorphic assessment to identify areas susceptible to inundation and erosion during outburst floods from Snow Lake. This dataset presents flood plain elevations above the approximate elevation of the main river channel low water surface.

This dataset provides time series for the ungaged watershed inflows and associated inflow points for the Lower Salinas Valley Hydrologic Models (SVHM), including the Salinas Valley Integrated Hydrologic Model (SVIHM) and the Salinas Valley Operational Model (SVOM). Monthly outflows from watersheds that do not have gages that surround the Salinas River Valley are used in the Lower Salinas Valley Hydrologic models are provided by the Salinas Valley Watershed Model (SVWM) (Hevesi and others, 2025) for the period from October 1, 1967 to September 30, 2018. The streams and tributaries that are not gaged and that are outside the active area simulated in the Lower Salinas Valley Hydrologic Models are provided as basin-wide estimates. The catchments are described as part of the surface water dataset (Henson and others, 2022). The surface inflows provided by the watershed inflows are used as part of the boundary conditions applied at model cells at the interface between outside of the model domain and within the active model domain. This data release contains a time series of input inflows for the 180 ungaged watersheds.

This data package includes 17,014 pairs of raster geotiffs. Each pair is made up of two geotiff rasters derived from historical observations from Landsat satellites (04-09) over the Yukon, Kuskokwim, and Tanana rivers in Alaska. One raster reports estimated mid-day water surface temperature (ST) in degrees Celsius (deg_Cc). The second raster reports the surface temperature quality assessment (sST_QA_c) and provides the ST product uncertainty (also in degrees). The period of observation is May through October for the years 1984-2022.

NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the National Tsunami Hazard Mitigation Program's (NTHMP) efforts to improve community preparedness and hazard mitigation. These integrated bathymetric-topographic DEMs are used to support tsunami and coastal inundation mapping. Bathymetric, topographic, and shoreline data used in DEM compilation are obtained from various sources, including NGDC, the U.S. National Ocean Service (NOS), the U.S. Geological Survey (USGS), the U.S. Army Corps of Engineers (USACE), the Federal Emergency Management Agency (FEMA), and other federal, state, and local government agencies, academic institutions, and private companies. DEMs are referenced to various vertical and horizontal datums depending on the specific modeling requirements of each State. For specific datum information on each DEM, refer to the appropriate DEM documentation. Cell sizes also vary depending on the specification required by modelers in each State, but typically range from 8/15 arc-second (~16 meters) to 8 arc-seconds (~240 meters).

This model archive contains the datasets, procedures, and necessary program code used to describe the Salinas Valley Watershed Model (SVWM). The SVWM simulates the daily historical water balance and hydrologic conditions for the Salinas Valley study area including the many un-gaged tributary subdrainages in the rugged and mountainous upland areas surrounding flat-lying valley lowlands coinciding with developed areas including croplands irrigated with groundwater. The SVWM simulates the natural hydrologic system for the entire Salinas Valley watershed and adjacent coastal basins, excluding anthropogenic components such as pumping, diversions, irrigation, and reservoir operations, for the 70 years beginning October 1, 1948, and ending September 30, 2022. The SVWM uses two modeling applications; the Hydrologic Simulation Program – Fortran (HSPF, version 12.4; U.S. Environmental Protection Agency, 2000) to simulate the natural hydrologic system (Bicknell and others., 2005) and the Basin Characterization Model (BCM; Flint and others, 2021) to develop spatially distributed, historical climate inputs for HSPF. The HSPF application simulates the daily surface water and shallow subsurface water storage and flow processes, including interception storage and evaporation on vegetation, surface retention storage and evaporation, pervious land soil water storage and evapotranspiration, runoff from impervious and pervious land areas, streamflow, recharge from pervious land areas, and recharge from streamflow seepage. Climate inputs developed using the BCM are daily precipitation, daily maximum and minimum air temperature, and daily potential evapotranspiration (PET) (Hevesi and others, 2022). SVWM parameters were estimated using geospatial data and then adjusted by trial-and-error fitting of simulated daily streamflow to long-term records of observed streamflow at 29 U.S. Geological Survey stream gages (U.S. Geological Survey, 2016) and to estimated daily surface water inflows to Nacimiento and San Antonio Reservoirs (Henson and others, 2022a). The trial-and-error calibration provided a good match between simulated and observed daily, monthly, mean-monthly, and annual streamflow. The simulated output components from the SVWM include evapotranspiration, land area runoff (overland flow, interflow, baseflow), recharge, and groundwater recharge for the 690 HRUs, as well as streamflow and stream seepage losses for the 690 stream reaches connecting the HRUs.