A crosswalk table between NHDPlus version 2.1 flowlines (using the unique field COMID) and the Watershed Boundary Dataset (WBD) 12-digit-hydrologic units (HU-12) is provided for the 48 contiguous United States. The crosswalk table provides a WBD HU-12 assignment for every networked flowline in the NHDPlus. In this way, the network developed for navigation and modeling, NHDPlus, is aligned with accounting units of the WBD HU-12s to the extent possible given the assumptions that were made in creating each. A crosswalk table for NHDPlus isolated sinks was produced by a simple overlay process where the sinks were assigned HU-12 values based on their position relative to the WBD snapshot HU-12s. This table was integrated with the flowline associations into one crosswalk table for both feature types. There is good alignment between aggregated NHDPlus catchments and WBD HU-12 units in many locations. These are areas where the flows and chemical or nutrient loads that are accumulated leave the HU-12 at a single outlet and are passed down to the next HU-12 downstream (or to the coast) as is assumed in the WBD model. A second pass through the data was made to account for any secondary outlet from each HU-12. The location of a secondary outlet with a significant drainage from that HU was identified in the alignment with NHDPlus. This resulted in a reduction in areas of mismatch as well as an improved crosswalk table. The crosswalk table should be used with caution in areas where efforts could be made to improve the data. For example, with medium-resolution NHD, a better definition of flow direction of the flowlines in Southern Florida would result in more flowlines being included in the “networked” flowlines with catchments, and that, in turn, would result in better alignment between NHDPlus catchments and HU-12s. Correcting errors in either the medium-resolution NHD or WBD would improve the alignment between the two datasets.

This tabular data set represents contact time, the length of time it takes for water to drain along subsurface flow paths to the stream, compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data for contact time was produced by Dave Wolock, (USGS, written communication, 2014) and based on the methods outlined in Wolock and others (1997). Units are days. Contact time is computed from basin topography, soil porosity, and soil hydraulic conductivity. Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).

This tabular data set represents contact time, the length of time it takes for water to drain along subsurface flow paths to the stream, compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data for contact time was produced by Dave Wolock, (USGS, written communication, 2014) and based on the methods outlined in Wolock and others (1997). Units are days. Contact time is computed from basin topography, soil porosity, and soil hydraulic conductivity. Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).

This tabular data set represents average depth to water table relative to the land surface(meters) compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data for average depth to water table from the land surface was produced by Ying Fan and others (written communication, Rutgers University, 2007). Units are meters from land surface. Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).

This tabular data set represents average depth to water table relative to the land surface(meters) compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data for average depth to water table from the land surface was produced by Ying Fan and others (written communication, Rutgers University, 2007). Units are meters from land surface. Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).

This tabular data set represents average depth to water table relative to the land surface(meters) compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data for average depth to water table from the land surface was produced by Ying Fan and others (written communication, Rutgers University, 2007). Units are meters from land surface. Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).

This tabular data set represents the percent of Hydrologic Landscape Regions compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data is the "Hydrologic landscape regions of the United States" produced by the United States Geological Survey (Wolock, 2003). Units are percent. The "Hydrologic landscape regions of the United States" are a 20-class classification scheme of noncontiguous regions (HLRs) built on the basis of similarities in land-surface form, geologic texture, and climate characteristics (Wolock, 2003). Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).

This tabular data set represents the percent of Hydrologic Landscape Regions compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data is the "Hydrologic landscape regions of the United States" produced by the United States Geological Survey (Wolock, 2003). Units are percent. The "Hydrologic landscape regions of the United States" are a 20-class classification scheme of noncontiguous regions (HLRs) built on the basis of similarities in land-surface form, geologic texture, and climate characteristics (Wolock, 2003). Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).

This dataset represents one of three derived outlets or "pour points" for each 12-digit hydrologic unit (HU12) in the Watershed Boundary Dataset (WBD) snapshot delivered with NHDPlus V2.1. The three related pour point locations, each delivered in a stand-alone dataset, are: "from" (fpp) and "to" (tpp) points that identify the location where flow leaves the HU12 polygon based on a flow direction raster, and a third "vector pour point" (vpp) selected "upstream" used to identify flow confluences near the "from" and "to" pour point locations. The points are derived from the NHDPlus V2.1 flow direction rasters and the WBD snapshot delivered with NHDPlus V2.1. This metadata document describes the "vector" pourpoints (vpp).

This tabular data set represents NLCD 2001 percent imperviousness compiled for two spatial components of the NHDPlus version 2 data suite (NHDPlusv2) for the conterminous United States; 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. This dataset can be linked to the NHDPlus version 2 data suite by the unique identifier COMID. The source data is the "NLCD 2001 Percent Developed Imperviousness (2011 Edition, amended 2014) - National Geospatial Data Asset (NGDA) Land Use Land Cover" which was produced by the United States Geological Survey (Yang and others, 2011). Units are percent. Reach catchment information characterizes data at the local scale. Reach catchments accumulated upstream through the river network characterizes cumulative upstream conditions. Network-accumulated values are computed using two methods, 1) divergence-routed and 2) total cumulative drainage area. Both approaches use a modified routing database to navigate the NHDPlus reach network to aggregate (accumulate) the metrics derived from the reach catchment scale. (Schwarz and Wieczorek, 2018).