Brakebill, J.W. Terziotti, S.E. 20110222 Version 1.0 vector digital data Reston, Virginia U.S. Geological Survey https://water.usgs.gov/lookup/getspatial?mrb_e2rf1 A digital hydrologic network was developed to support SPAtially Referenced Regression on Watershed attributes (SPARROW) models within selected regions of the United States. These regions correspond with the U.S. Geological Survey's National Water Quality Assessment (NAWQA) Program Major River Basin (MRB) study units 2, 3, 4, 5, and 7 (Preston and others, 2009). MRB2, covers the South Atlantic-Gulf and Tennessee River basins. MRB3, covers the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins. MRB4, covers the Missouri River basins. MRB5, covers the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins. MRB7, covers the Pacific Northwest River basins. The digital hydrologic network described here represents surface-water pathways (MRB_E2RF1) and associated catchments (MRB_E2RF1WS). It serves as the fundamental framework to spatially reference and summarize explanatory information supporting nutrient SPARROW models (Brakebill and others, 2011; Wieczorek and LaMotte, 2011). The principal geospatial dataset used to support this regional effort was based on an enhanced version of a 1:500,000 scale digital stream-reach network (ERF1_2) (Nolan et al., 2002). Enhancements included associating over 3,500 water-quality monitoring sites to the reach network, improving physical locations of stream reaches at or near monitoring locations, and generating drainage catchments based on 100m elevation data. A unique number (MRB_ID) identifies each reach as a single unit. This unique number is also shared by the catchment area drained by the reach, thus spatially linking the hydrologically connected streams and the respective drainage area characteristics. In addition, other relevant physical, environmental, and monitoring information can be associated to the common network and accessed using the unique identification number. The purpose of this dataset was to provide a framework to spatially reference and summarize explanatory information supporting nutrient SPARROW models in selected regions of the conterminous United States. The digital hydrologic network also is used to map spatial distributions of nutrient predictions provided by SPARROW. In addition, the topology of this hydrologically connected network allows for the simulation of water movement, providing the ability to accumulate flow and route constituents throughout the river network. Although developed and modified specifically for SPARROW modeling applications, the dataset is suitable for other large-scale watershed studies and applications. The ERF1_2 stream-reach geospatial dataset, modified from the 1:500,000 U.S. Environmental Protection Agency (USEPA) River Reach File (RF1) (Nolan et al., 2002) was the base stream-reach network for nutrient SPARROW models developed in MRB's 2, 3, 4, 5, and 7. After modifications described in this metadata, the resulting stream-reach dataset supporting MRB SPARROW modeling for the above MRBs is referred to as MRB_E2RF1. A set of measured constituent loads at monitoring stations in streams representing a wide variety of watershed conditions is a primary requirement for regional SPARROW model calibration. (Schwarz et al, 2006). Site location and water quality data were assembled and annual nutrient loads were computed for the period from 1970 to 2007 using methods described in Saad, 2010. Over 3,500 water-quality monitoring sites were evaluated for referencing on the digital stream network MRB_E2RF1. A drainage boundary (catchment) associated with each stream reach (in MRB_E2RF1) in the conterminous U.S. was delineated to create an area or zone for summarizing watershed characteristics. The catchment data set is named mrb_e2rf1ws. The term catchment refers to the local area that drains directly to a stream reach. These catchment characteristics are typically generated using GIS "overlay" and "combine" operations. Calculations usually include mean or accumulated values but also can include categorical values. Other catchment characteristics include local and total drainage area and the number of reservoir impoundments within a local catchment (Wieczorek and LaMotte, 2011). Because each MRB study unit was at different phases of the project when the reach network was being compiled, the hydrologic sequencing attribute (HYDSEQ) for each reach was calculated separately and independently within each MRB. The result is a sequencing number that lacks national consistency, a limitation when performing national applications that require hydrologic ordering. However, for this dataset (MRB_E2RF1), a new hydrologic sequence was calculated that included all reaches nationally and may differ from that actually used for MRB SPARROW modeling. All processing steps were performed using ArcInfo Workstation, Arcedit, and GRID. An overview of reach networks supporting SPARROW modeling can be found in Brakebill and others, 2011. Details of data processing are found in the Processing_Steps of this metadata. 20110201 publication date Complete None planned -127.859452 -65.377389 51.549102 23.243486 USGS Thesaurus stream river network SPARROW reach RF1 water quality reservoir inlandWaters NAWQA MRB ISO 19115 Topic Category geoscientificInformation inlandWaters environment USGS Metadata Identifier USGS:fe42737d-1f29-4777-a110-dafc8f4675a3 Geographic Names Information System Conterminous United States Major River Basin MRB2 MRB3 MRB4 MRB5 MRB7 none Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology. John W. Brakebill U.S. Geological Survey mailing address

5522 Research Park Drive

Baltimore MD 21228 USA 443-498-5557 443-498-5510 jwbrakeb@usgs.gov https://water.usgs.gov/GIS/browse/mrb_e2rf1.jpg Illustration of the dataset jpg U.S. Geological Survey Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.3.1.3500 U.S. Environmental Protection Agency 19960101 vector digital data Washington, D.C. U.S. Environmental Protection Agency http://www.epa.gov/waters/doc/rf1_meta.html Richard B. Alexander, John W. Brakebill, Robert E. Brew, and Richard A. Smith 19990228 vector digital data U.S. Geological Survey Open File Report 99-457 Reston, Virginia U.S. Geological Survey https://water.usgs.gov/lookup/getspatial?erf1 Nolan, J.V. Brakebill, J.W. Alexander, R.B. Schwarz, G.E. 2002 2.0 vector digital data Open-File Report 02-40 Reston, Virginia U.S. Geological Survey https://water.usgs.gov/GIS/metadata/usgswrd/XML/erf1_2.xml Brakebill, J.W. Wolock, D. M. Terziotti, S.E. 2011 document JAWRA In Press Middleburg, Va. John Wiley & Sons See processing steps and below. This data set is believed to provide complete and accurate hydrologic connectivity among the streams represented. Vectors (arcs) representing streams are intended to be presented in an FNODE to TNODE orientation or a downstream direction. Several quality control steps were applied to test the accuracy of the delineated stream reach catchment areas. Catchments that were not considered valid based on visual inspection were edited and corrected. In addition to visual checks against elevation data and known hydrologic basin divides, two major quality-control steps were taken: (1) checking that a catchment was generated for each stream reach, and (2) checking that the accumulated areas of catchments upstream of associated monitoring stations were within twenty percent of published drainage areas for the monitoring site. Generally, three reasons can account for a discrepancy in drainage area comparisons: the stream reaches were improperly registered or digitized so that there was a misalignment with the elevation data, causing the enforcement of drainage to be inaccurate (the most common source of discrepancy); the elevation data were inaccurate; or the published drainage area values were incorrect. Corrections were done to either the stream reach network, the elevation data, or to the drainage area value. The set of streams represented reflects the choices in the U.S. Environmental Protection Agency's RF1 (USEPA 1996). In previous versions (ERF1 and ERF1_2), reservoir and lake boundaries were removed from the original RF1 data set. They are represented by a single trace to satisfy the connectivity requirements of the dataset. Centerlines were manually delineated within the RF1 shoreline boundaries (Alexander and others, 1999). The centerline reaches approximate the thalweg of each reservoir or lake. Shorelines of major estuaries and some coastal areas were added to the data set to serve as a terminal locations for trace routines. Existing reaches extending within estuaries were deleted. Reach 57115 (MRB_ID = 57115) does not have an independent catchment. The drainage area was merged with catchment 57117. None performed Brakebill, J.W. Preston, S.D. 2003 document Watershed. Environmental Monitoring and Assessment Kluwer Academic Publishers 81:73-84 Pensacola, Fl. USEPA http://md.water.usgs.gov/gis/chesbay/sparrow2/doc/08-Brakebill.pdf online 2003 publication date Brakebill and Preston, 2003 Procedure Brakebill, J.W. Wolock, D.M. Terziotti, S.E. 2011 Journal American Water Resources Association document online 2011 publication date Brakebill and others, 2011 Applications of hydrologic networks Falcone, James 2003 raster digital data Written communication Written communication Reston, Virginia U.S. Geological Survey online 2003 publication date Falcone, 2003 Digital elevation Hellweger, F.L Maidment, D.R. 1997 Computer Program Austin, Texas University of Texas http://www.crwr.utexas.edu/gis/gishyd98/quality/agree/agree.htm computer program 1997 publication date Hellweger and Maidment, 1997 Agree.aml program to "burn" streams into DEM Jarvis, A. Reuter, H.I. Nelson, A. Guevarra, E. 2008 raster digital data Canada The CGIAR Consortium for Spatial Information http://srtm.csi.cgiar.org/ online 2008 publication date Jarvis and others, 2008 Digital elevation outside of US Nolan, J.V. Brakebill, J.W. Alexander, R.B. Schwarz, G.E. 2002 vector digital data Open-File Report 02-40 Reston, Virginia U.S. Geological Survey https://water.usgs.gov/GIS/metadata/usgswrd/XML/erf1_2.xml online 2002 publication date Nolan and others, 2002 ArcInfo coverage of stream reaches Preston, S.D. Alexander, R.B. Woodside, M.D. Hamilton, P.A. 2009 document Fact Sheet 2009-3019 Reston, Virginia U.S. Geological Survey https://pubs.usgs.gov/fs/2009/3019/ online 2009 publication date Preston and others, 2009 SPARROW description and applications Saad, D.A. Schwarz, G.E. Robertson, D.E. Booth, N.L. 2011 document JAWRA unspecified Midleburg, Va. John Wiley and Sons online 2011 publication date Saad and others, 2011 Water-quality monitoring screening techniques and site selection Saunders, W. 2000 document Maidment, D.R. Djokic, D. 2000 document Redlands, CA. ESRI Press p. 29-51 paper 2000 publication date Saunders, 2000 DEM preparation techniques Schwarz, G.E. Hoos, A.B. Alexander, R.B. Smith, R.A. 2006 document Techniques and Methods Book 6, Section B. Chapter 3, 248 p Reston, Virginia U.S. Geological Survey https://pubs.usgs.gov/tm/2006/tm6b3/ online 2006 publication date Schwarz and others, 2006 SPARROW documentation USEPA (U.S. Environmental Protection Agency) USGS (U.S. Geological Survey) 2005 vector digital data ftp://ftp.horizon-systems.com/NHDPlus/documentation/metadata.pdf online 2005 publication date USEPA and USGS, 2005 Medium resolution NHDPlus, value added attributes and visual spatial detail USGS (U.S. Geological Survey) 2009 document Fact Sheet 2009-3053 Rolla, Mo. U.S. Geological Survey https://pubs.usgs.gov/fs/2009/3053/ online 2009 publication date USGS, 2009 30m elevation data U.S. Geological Survey 2008 tabular digital data http://waterdata.usgs.gov/nwis online 2008 publication date USGS, 2008 Water-quality site information Wieczorek, M.E. LaMotte, A. 2011 tabular digital data https://water.usgs.gov/nawqa/modeling/rf1attributes.html online 2011 publication date Wieczorek and LaMotte, 2011 Spatial data associated to the network 1) Creating a stream-reach network: (MRB_E2RF1) The dataset ERF1_2 was downloaded from https://water.usgs.gov/GIS/metadata/usgswrd/XML/erf1_2.xml and renamed to MRB_E2RF1. Initially, all of the existing attributes in ERF1_2 were maintained, including the unique reach identification fields used in prior national SPARROW applications. A new unique stream reach identification field (MRB_ID), was added (ADDITEM) to the newly created MRB_E2RF1 stream-reach dataset to facilitate the association of additional water-quality monitoring stations to the data. This is the variable that provides a link to associated catchments and other explanatory data associated to the network. In order to maintain additional connections to previous national SPARROW model applications, the initial value for the attribute MRB_ID was set to the value of the previously used unique identification number (E2RF1## ) (Nolan et al., 2002). Ninety-meter Shuttle Radar Topography Mission (SRTM) (Jarvis and all, 2008) elevation data RESAMPLED to 100-meters were used to delineate stream networks in areas of Canada and Mexico that contribute flow into the United States. In addition, some reaches were created to provide accurate drainage patterns flowing away from the United States in order to later produce a more accurate drainage divide. These reaches were created strictly for the use of catchment generation described later. NIBBLE was used to fill no data values with neighboring elevation values. FLOWACCUMULATION was performed on the elevation data, where a threshold of 5000 accumulated cells constituted a stream reach. This produced a stream network representing foreign drainage (Canada and Mexico) consistent with the stream density of the MRB_E2RF1 data. These stream reaches representing foreign drainages were connected to the existing MRB_E2RF1 reaches to produce a continuous stream network. The reaches representing foreign drainages were populated with the unique identifier (MRB_ID) value not previously used in the United States. Isolated networks were connected using NHDPlus flowlines (ArcEdit, PUT). These reaches also were populated with the unique identifier (MRB_ID) value not previously used in the data set. Topography was established using the BUILD command. Attributes were evaluated and populated based on visual inspection with USGS DRG's and the NHDPlus flowlines, and computations. These attributes include RCHTOT, RCHTYPE, CANADIAN, TERMFLAG, HEADFLAG, HYDSEQ, and MRB. These attributes are describe in the attribute report section. A raster representation of the stream network (MRB_E2RF1) with the unique identifier (MRB_ID) of each stream reach as the cell value was created using a 100-meter cell resolution and the LINEGRID command. This data was used for "stream burning" describe later in the processing steps. 2006 2) Associating Monitoring data: Six regional nutrient datasets were compiled for use in each of the MRB study unit SPARROW models (Saad et al., 2010). Locations of each water-quality monitoring station were used to associate the site on the appropriate stream reach of the National Hydrography Dataset Plus (NHDPlus) dataset (USEPA and USGS, 2005) and subsequently on MRB_E2RF1. The Arc Workstation command "NEAR" was used with a threshold of 2000 meters to assign each water-quality station to an NHDPlus flowline..Because NHDPlus is more spatially detailed than MRB_E2RF1, the data provided good spatial orientation and visualization. Visual inspections and comparisons with NHDPlus flowline stream and station name were completed by each MRB unit to validate the association. Corrections to the station location information were made if the site were determined to be miss-located. Once sites were associated with NHDPlus flowlines, a semi-automated process in ArcEdit and AML was used to locate monitoring sites on MRB_E2RF1 reaches. Each station was evaluated individually to verify if it had been associated previously to the network (ERF1_2). The station identification number (STAID) maintained in the stream-reach dataset and the newly created geospatial dataset of water-quality stations was used for this validation process. If the monitoring station had been previously associated to ERF1_2 and subsequently MRB_E2RF1, then no further action was required. If not, a visual inspection of the station location, the hydrologic features (flowlines) in the NHDPlus dataset, and the MRB_E2RF1 dataset within a GIS was performed. This visual inspection also utilized station name, stream name, and distance from the reach to the monitoring station. If the station was within 250 meters of the MRB_E2RF1 reach based on the NEAR command, and the stream and station name were determined to be consistent, then the station was associated with that reach. If the station was greater than 250 m from the reach, then manual (visual) methods were used to locate the station based on an evaluation of the stream and station names. In some instances, the location of the station was considered inaccurate, and the location of the station was adjusted (ArcEdit, MOVE). In other instances, it was determined that the station did not fall on a stream reach at this scale (1:500,000) and, therefore, would not be used for the SPARROW model application.. Associating a monitoring station with a MRB_E2RF1 reach required the placement of a new stream network node at the location of the monitoring station along the reach. This essentially "split" the existing reach into two separate reaches (Brakebill and Preston, 2003). Once a reach was split, (Arcedit, SPLIT) the monitoring station identification number was assigned to the upstream reach. The unique identification number (MRB_ID) also was modified (calculated as a new value starting with a value of 90,000). Because the existing reach was split into two separate reaches, the travel time, which is a function of the reach length and stream velocity, was recalculated. The process of locating monitoring stations on MRB_E2RF1 stream reaches identified additional issues that needed to be addressed. In some cases, water-quality stations were originally incorrectly located on the NHDPlus network, and subsequently MRB_E2RF1. These sites were manually relocated (ArcEdit, MOVE) to the appropriate reach. Some sites were co-located with other non-USGS agency sites but with different station identification numbers. In these situations, the station that measured water-quality information more suitable for load estimation was retained. In some cases, MRB_E2RF1 reaches were manually altered to better represent the stream channels at or near the location of the monitoring site. This insured that accurate catchments at or near the monitoring stations would be created. Manual editing involved moving the vertices of the stream reach to better match the stream locations represented by NHDPlus flowlines (ArcEdit, VERTEX MOVE). 2006 3) Catchment Generation: MRB_E2RF1WS Three 100-meter resolution surface elevation grids were acquired (Falcone, 2003, based on re-sampled National Elevation Dataset (NED) (USGS, 2009)) representing eastern, central, and western sections of the United States (US). Elevation cells with missing data were estimated using NIBBLE and values from nearest neighbor cells. The three US elevation grids and the SRTM based international elevation data described earlier were MERGED into a single digital elevation model (DEM). The elevation data were forced to conform to the drainage patterns defined by the raster representation of the MRB_E2RF1 stream reaches. This was accomplished by insertion of a raster representation of the streams into the elevation data. This process, also referred to as "stream burning" (Saunders, 2000) uses a tool (AGREE.AML) developed by Hellweger and Maidment (1997) to create an artificially low stream channel to ensure that the elevation surface would flow towards the stream segments. Depressions and sinks were removed from the elevation dataset and the stream network patterns were incorporated into the DEM using NIBBLE and the nearest elevation values. The conterminous United States was divided into eight regions to expedite the catchment generation process. These regions coincided with MRB study unit boundaries (Preston et al., 2009). FLOWDIRECTION was used to compute the flow patterns (direction of flow based of surface elevation) throughout the network within each region. Catchments for each set of unique cell values (MRB_ID) from the raster representation of the stream network were created using the WATERSHED function in each of the 8 regions. The catchment grids from the MRB study units were then MERGED to form a national representation of catchments (MRB_E2RF1WS). To verify that each stream reach had a representative catchment, the database relations based on the unique identification numbers for each reach and catchment were used as a common field. Because each catchment was tagged with the unique identifier of the stream reach it drained, a direct relation between the two geospatial data layers exists. Unmatched records based on the identification numbers relation identified missing catchments. If a catchment was not created, it was typically because the stream-reach length was less than 100m (the cell resolution of the elevation data used to create the catchment). A stream reach shorter than 100m may not have had a catchment delineated because the function that creates a raster representation of the stream reaches assigned the elevation cell to the longer reach within the same elevation cell. The raster catchment layer was then manually edited (GRIDEDIT, FILLCELL) to add a one cell representation of the stream reach. In some cases, legacy issues with the base stream-reach network (Nolan et al., 2002) caused the watershed functions to create erroneous catchment delineations. These situations included reaches starting and stopping at the same nodes, forming a loop, or reaches that were partially overlapping each other, i.e., occupying the same space but having different identification values. As legacy issues were discovered, overlapping arcs were deleted so that a clean network could be used for catchment creation. To validate the accumulated drainage areas upstream of the monitoring sites, the stream network was traced upstream from each site using the topological information in the network. The stream reaches that were upstream of a monitoring site were identified and the associated catchments were selected. The sum of the areas of the selected catchments (DEMTAREA) was compared to the published drainage area value reported in either the USGS National Water Information System (NWIS) (USGS, 2008) or in a State or USEPA database. If the drainage area values differed by 20% or more, then the stream reach and associated catchments were further evaluated to determine the source of the discrepancy. Corrections to the stream reach network were necessary when the stream reaches were misaligned with the elevation data. These situations occurred when mapped streams crossed ridges and major drainage divides rather than follow the natural flow direction. In some cases these were obvious occurrences such as a straight line connecting two nodes, rather than following any topographic features. In many cases however, the streams needed to be visually compared with either digital raster graphics (DRG's - the digital representation of a 1:24,000-scale topographic map) or to NHDPlus flowlines. Two methods were used for correcting the catchments associated with the reaches based on drainage area comparisons. If major changes to the reach network were needed, then the stream reaches were burned into the elevation data again and new catchments were delineated. This occurred in MRB study areas 3 and 4. If only small areas were edited, then the raster representation of the catchments was edited manually (GRIDEDIT and FILLVALUE and FILLCELL) to reflect the drainage area of the new stream paths. Manual edits included changing the value of cells to represent the correct catchment area. In the cases where the elevation data were inaccurate, manual edits to the catchments were necessary using Digital Raster Graphics (DRG's) as a visual guide. 2007 4) Attribute simplification: MRB_E2RF1 In order to simplify the data structure, only attributes used in the MRB SPARROW modeling were maintained. Attributes in the reach file used in prior SPARROW modeling efforts were dropped (DROPITEM). The exceptions are listed in the attribute section of this metadata. In previous SPARROW model applications, MRB2 adopted abbreviations for some monitoring station identifications in the reach network. Those abbreviations were discarded, and the actual monitoring station identification numbers are identified in this data set. 2010 Vector Complete chain 66157 Node, planar graph 66613 Albers Conical Equal Area 29.500000 45.500000 -96.000000 23.000000 0.000000 0.000000 coordinate pair 10.000000 10.000000 meters North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 mrb_e2rf1.aat Arc attribute table Automatically created FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. FNODE# Internal node number for the beginning of an arc (from-node). ESRI Whole numbers that are automatically generated. TNODE# Internal node number for the end of an arc (to-node). ESRI Whole numbers that are automatically generated. LPOLY# Internal node number for the left polygon. ESRI Whole numbers that are automatically generated. RPOLY# Internal node number for the right polygon. ESRI Whole numbers that are automatically generated. LENGTH Length of feature in internal units. ESRI Positive real numbers that are automatically generated. MRB_E2RF1# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. MRB_E2RF1-ID User-defined feature number. ESRI Sequential unique whole numbers that are automatically generated. HUC 8-digit USGS Hydrologic cataloging unit of the reach. ERF1_2 8 character Hydrologic Unit code unspecified unspecified PNAME Name of the reach defined in RF1. ERF1_2 character unspecified unspecified RCHTYPE Code determining reservoir or non-reservoir reach. ERF1_2 0 Non-reservoir reach unspecified 1 Interior reservoir reach Visually identified 2 Outlet reservoir reach Visually identified ERF1 Unique key identifying the reach Version 1 files. ERF1 1.2 Positive whole numbers uniquely defined unspecified unspecified E2RF1 Unique reach identification number for Version 2.0. ERF1_2 Positive whole numbers uniquely defined unspecified unspecified STAID Monitoring station identification number MRB Study Units 20 characters describing station identifiecation unspecified unspecified MEANQ Mean streamflow for reach, in cubic feet per second. ERF1_2 .00001 634,071.1875 Cubic feet per second, -9999 = no data MEANV Velocity corresponding to mean streamflow for reach, in feet per second ERF1_2 .00001 7.96 Feet per second, -9999 = no data FRAC Fractional diversion of load for reaches that share to-nodes. ERF1_2 0 1 Fraction STATE1 State FIPS (Federal Information Processing Standard) code. ERF1_2 Integer 2-digit state codes defined uniquely unspecified unspecified RCHTOT Reach water time of travel (days). Calculated, RCHTOT = C1 * MEANV / LENGTH, where C1 is a conversion factor of .00003797 ft-day/meter-second 0 17.226721 Days, -9999 = no data TERMFLAG Code determining termination of transport. Visually determined 0 Transport reach unspecified 1 Terminal Visually identified 2 Non-connected, closed basin, of draining into Canada Visually identified 3 Shoreline reaches Visually identified 4 Canadian boundary reach Visually identified EDACDA NOAA Estuary code ERF1_2 ERF1 character code NOAA estuary character code MRB_E2RF1 EDANAME NOAA estuary name Erf1_2 ERF1 character name NOAA estuary character name MRB_E2RF1 HEADFLAG Headwater reach flag. unspecified 0 Non-headwater reach unspecified 1 Headwater reach Hydseq program DEMIAREA Incremental drainage area for a given reach, in square kilometers. Catchment boundaries (MRB_E2RF1WS) .01 67,843.1875 Square kilometers DEMTAREA Total drainage areas upstream summed for a given reach, in square kilometers (sum of DEMIAREA). Catchment boundaries, HYDSEQ program. .01 3,200,693.25 Square kilometers HYDSEQ Hydrologoc sequence number for use in sorting the file in downstream order to perform network operations (e.g., summation of reach drainage area). HYDSEQ program. Sequential unique whole numbers that are automatically generated. MRB_ID Unique reach identification number for this dataset. Used to relate ancillary data for 2002 MRB nutrient SPARROW models. ERF1_2 and Processing Steps 1 664,620 STD_ID Unique reach identification number prior to station monitoring and reach splitting for this dataset. ERF1_2 0 81,901 LOCAL_SAME Flag identifying a split reach for this version. ERF1_2 0 Reach remains same from ERF1_2 unspecified 1 Reach was split from ERF1_2 unspecified MRB NAWQA Major River Basin code. MRB Study Units 1 MRB1, New England and Mid-Atlantic River basins MRB Study Units 2 MRB2, South Atlantic-Gulf and Tennessee River basins MRB Study Units 3 MRB3, Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins MRB Study Units 4 MRB4, Missouri River basin MRB Study Units 5 MRB5, Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins MRB Study Units 6 MRB6, Southwestern basins MRB Study Units 7 MRB7 Pacific Northwest River basins MRB Study Units 8 MRB8, California basins MRB Study Units CANADIAN Flag identifying Canadian reaches. Visually Determined 0 Non-Canadian unspecified 1 Canadian unspecified HUC2 2-digit USGS Hydrologic cataloging unit. ERF1_2 2 character Hydrologic Unit code MRB_E2RF1 HUC4 4-digit USGS Hydrologic cataloging unit. ERF1_2 4 character Hydrologic Unit code MRB_E2RF1 HUC6 6-digit USGS Hydrologic cataloging unit. ERF1_2 6 character Hydrologic Unit code MRB_E2RF1 mrb_e2rf1.nat Node attribute table Automatically created FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. mrb_e2rf1.nat Node attribute table Automatically created FID Internal feature number ESRI FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. ARC# Internal sequence number Automatically created Coordinates defining the features. MRB_E2RF1# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. MRB_E2RF1-ID User-defined feature number. ESRI Sequential unique whole numbers that are automatically generated. STAID Station Identification User Defined Character unspecified unspecified MRB MRB study unit number MRB study units Same as arc attribute table Same as arc attribute table Same as arc attribute table MRB_ID is the unique reach identification number that links the catchments (MRB_E2RF1WS), SPARROW model predictions and results, and associated referenced data found in Wieczorek and LaMotte, 2011. none U.S. Geological Survey Michael Ierardi IT Specialist mailing and physical

445 National Center

Reston Virginia 20192 USA 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov Downloadable Data Although this data set has been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Export Vector Reach Network, Full coverage zipped 45936 https://water.usgs.gov/GIS/dsdl/mrb_e2rf1.zip None. This dataset is provided by USGS as a public service. 20201117 U.S. Geological Survey Michael Ierardi IT Specialist mailing and physical address

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998