This data set is a digital hydrologic unit boundary layer that is at the Subwatershed (12-digit) level. The original data set was developed by delineating the boundary lines on base USGS 1:24000 scale topographic quadrangle, and digitizing the delineated lines. Digital Raster Graphics (DRG) images were used for edits to the data layer. This data set consists of geo-referenced digital map data and attribute data. The spatial data are in a statewide coverage format and include complete coverage of the entire state of Connecticut, and small parts of surrounding states. The hydrologic unit ID code attached to each delineated polygon is linked to the attribute data.
publication date
Attribute field (item) names need to be spelled exactly as shown and in the order specified. Required attributes must be populated unless fields are optional, in those cases, leave the field blank. The attribute schema is illustrated for Environmental Systems Research Institute (ESRI) software1. If another software is being used other than ArcInfo or ArcView, please follow the ArcInfo format. For field width in ArcView, please create the fields according to the width specified under "Output" in the descriptions below. All the fields listed below are required in each state dataset, but, a state may add additional fields to their own dataset. If there are any questions, contact the National Cartography & Geospatial Center for assistance. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
Populate this field with the hydrologic unit type from the list provided that most closely identifies the subwatershed. Use any of the one digit abbreviations in uppercase that is provided in the list. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
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| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
Feature geometry. (Source: ESRI)
A unique 8-digit code from the USGS map series "Hydrologic Unit Maps". Use the existing code for the sub-basin where the subwatershed resides; do not change this code. The same number should be used in every record that pertains to a subwatershed that resides within the same 8-digit sub-basin. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
This field provides a unique 10-digit code for each watershed. Add two digits to the end of the existing 8-digit code, therefore resulting in a 10-digit number. This same number should be used in every record that pertains to a subwatershed that resides within the same 10-digit watershed. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
This field provides a unique 12-digit code for each subwatershed. Add two digits to the end of the existing 10-digit code, therefore creating a 12-digit number. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
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| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
Area of subwatershed including non-contributing areas calculated to acres as a whole number, no decimals. The "Acres" field needs to be calculated from the "Area" field. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
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| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
The "States" field needs to include the names of all state(s) that the subwatershed falls within. Use the 2-digit postal abbreviation in upper case and sort the state(s) in alphabetical order. If using more then one abbreviation, separate with a comma with no space after the comma. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
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| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
Drainage areas that do not flow toward the outlet of any hydrologic unit are considered non-contributing. If a non-contributing area is on the boundary between two or more hydrologic units, determine the low point along the non-contributing area boundary. The non-contributing area should be associated with the hydrologic unit adjacent to the low point on the boundary. This attribute should be the total of the non-contributing areas within a hydrologic unit calculated in acres. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
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| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
Populate this field with the 10-digit code of the 5th level hydrologic unit that is receiving the majority of the flow from the watershed that the 6th level HU falls within. Outlets created by ditching or other artificial drainage are not to be considered for this field. If the 5th level HU empties directly to the ocean and not to another hydrologic unit, the word, "ocean", is used in this field. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
This field is for officially recognized names only. Populate this field by following the directions in subsection 6.3 "Watershed and Subwatershed Naming Protocol". Populate this field with the identical name for all 6th level hydrologic units that fall within the same 10-digit HU. The name used to attribute the watershed should be used only once within a 4th level unit. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
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| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
This field should identify any type of modifications to natural overland flow present in the 10-digit watershed. In the attribute field, identify from most significant to least significant modification(s). Use one or more of the following abbreviations in uppercase to identify your modification(s). If using more then one abbreviation, separate with a comma with no space after the comma. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
Populate this field with the hydrologic unit type from the list provided that most closely identifies the watershed. Use any of the one-digit abbreviations in uppercase that is provided in the list. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
Populate this field with the 12-digit code of the 6th level hydrologic unit that is receiving the majority of the flow from the subwatershed. Outlets created by ditching or other artificial drainage are not to be considered for this field. If the 6th level HU empties directly to the ocean and not to another hydrologic unit, the word, "ocean", is used in this field. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
This field should identify any type of modifications to natural overland flow present in the 12-digit subwatershed. In the attribute field, identify from most significant to least significant modification(s). Use one or more of the following abbreviations in uppercase to identify your modification(s). If using more than one abbreviation, separate with a comma with no space after the comma. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
This field is for officially recognized names only. Populate this field by following the directions in subsection 6.3 "Watershed and Subwatershed Naming Protocol". The name used to attribute the subwatershed should be used only once within a 5th level unit. (Source: Federal Standards for Delineation of Hydrologic Unit Boundaries - FGDC Proposal, Version 1.0)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Standards for Delineation of Hydrologic Unit Boundaries, FGDC Proposal, Version 1.0 |
| Codeset source: | Please refer to the Entity and Attribute Overview for valid values and definitions |
Hydrologic Unit delineations are closed polygons that encompass all area draining toward the lowest point (called outlet) in the polygon. Because of nominal sizes for the different hydrologic unit levels (Watershed (40,000 to 250,000 acres) and Subwatershed (3,000 minimum, generally 10,000 to 40,000 acres)), some polygons do not include all areas up to the drainage divide but all areas to one or more other upstream hydrologic units. A unique hydrologic unit code is used to identify each hydrologic unit. The Watershed hydrologic unit codes start with the 8-digit Subbasin (Cataloging Unit) number that contains the Watershed. Likewise the Subwatershed hydrologic unit codes start with the 10-digit Watershed number that contains the Subwatershed. A map unit symbol uniquely identifies each closed polygon. Each symbol is linked to a hydrologic unit code. The uniqueness of hydrologic unit codes while applying to hydrologic units does not carry over to polygons. Small islands offshore in coastal and lakeshore areas or in river deltas are given the same code as adjacent hydrologic units on the mainland. Attribute data associated with a hydrologic unit code includes: non-contributing area (acres); names for each level of nesting (region, subregion, basin, subbasin, watershed and subwatershed); codes for hydrologic units immediately downstream; name of town where subwatershed outlet occurs; information about type of subwatershed or watershed; reference to human-caused modifications to stream flow within the watershed; notes concerning delineation of hydrologic unit boundary. Description of attributes by field from the Federal Standards for Delineation of Hydrologic Unit Boundaries 1) .pat attributes Huc_8 : Eight Digit Hydrologic Unit Code - (REQUIRED) A unique 8-digit code from the USGS map series "Hydrologic Unit Maps". Use the existing code for the sub-basin where the subwatershed resides; do not change this code. The same number should be used in every record that pertains to a subwatershed that resides within the same 8-digit sub-basin.Numbers were assigned in an upstream to downstream fashion. Where no downstream/upstream relationship could be determined numbers were assigned in a clockwise fashion. Huc_10: Ten Digit Hydrologic Unit Code - (REQUIRED) This field provides a unique 10-digit code for each watershed. Add two digits to the end of the existing 8-digit code, therefore resulting in a 10-digit number. This same number should be used in every record that pertains to a subwatershed that resides within the same 10-digit watershed.Numbers were assigned in an upstream to downstream fashion. Where no downstream/upstream relationship could be determined numbers were assigned in a clockwise fashion. It should be noted that the polygons that cross into Idaho were numbered by Idaho and are not consistent with the above methods. Affected huc_8s include: 17040202, 17040204 and 17040104. Huc_12: Twelve Digit Hydrologic Unit Code - (REQUIRED) This field provides a unique 12-digit code for each subwatershed. Add two digits to the end of the existing 10-digit code, therefore creating a 12-digit number.Numbers were assigned in an upstream to downstream fashion. Where no downstream/upstream relationship could be determined numbers were assigned in a clockwise fashion. It should be noted that the polygons that cross into Idaho were numbered by Idaho and are not consistent with the above methods. Affected huc_8s include: 17040202, 17040204 and 17040104. Acres: Acres - (REQUIRED) Area of subwatershed including non-contributing areas calculated to acres as a whole number, no decimals. The "Acres" field needs to be calculated from the "Area" field. States: States - (REQUIRED) The "States" field needs to include the names of all state(s) that the subwatershed falls within. Use the 2-digit postal abbreviation in upper case and sort the state(s) in alphabetical order. If using more then one abbreviation, separate with a comma with no space after the comma. Ncontrb_a: Non-Contributing Area - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) Drainage areas that do not flow toward the outlet of any hydrologic unit are considered non-contributing. If a non-contributing area is on the boundary between two or more hydrologic units, determine the low point along the non-contributing area boundary. The non-contributing area should be associated with the hydrologic unit adjacent to the low point on the boundary. This attribute should be the total of the non-contributing areas within a hydrologic unit calculated in acres. Hu_10_ds: Fifth Level Downstream Hydrologic Unit Code - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) Populate this field with the 10-digit code of the 5th level hydrologic unit that is receiving the majority of the flow from the watershed that the 6th level HU falls within. Outlets created by ditching or other artificial drainage are not to be considered for this field. If an HU flows into an ocean or the Gulf of Mexico populate this field with "OCEAN" and if a HU flows into one of the Great Lakes use the term "LAKE". If a HU flows across international borders use "CANADA" or "MEXICO" depending on which country the HU drains into. If an HU is a closed basin, then populate this record with the term "CLOSED BASIN". Hu_10_name: Fifth Level Hydrologic Unit Name - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) This field is for officially recognized names only. Populate this field by following the directions in subsection 6.3 "Watershed and Subwatershed Naming Protocol". Populate this field with the identical name for all 6th level hydrologic units that fall within the same 10-digit HU. The name used to attribute the watershed should be used only once within a 4th level unit. Some 10-digit HU were assigned the huc_10 number when no GNIS name was identified on the DRG-Es. Hu_10_mod: Fifth Level Hydrologic Unit Modifications - (REQUIRED) This field should identify any type of modifications to natural overland flow that alters the location of the hydrologic unit boundary for a 10-digit watershed. In the attribute field, identify from most significant to least significant modification(s). Use one or more of the following abbreviations in uppercase to identify your modification(s). If using more then one abbreviation, separate with a comma with no space after the comma. SC - Stormwater Canal ID - Irrigation Ditch IT - Interbasin Transfer BC - Barge Canal SD - Stormwater Ditch PD - Pipe Diversion CD - Channel Diversion NC - Non-Contributing KA - Karst LE - Levee NM - No Modifications OC - Overflow Channel DM - Dam at outlet or HU boundary OT - Other Hu_10_type: Fifth Level Hydrologic Unit Type - (REQUIRED) Populate this field with the hydrologic unit type from the list provided that most closely identifies the watershed. Use any of the one-digit abbreviations in uppercase that is provided in the list. S - "Standard" hydrologic unit - Any land HU with drainage flowing to a single outlet point, excluding non-contributing areas. This includes areas or small triangular wedges between adjacent HU's that remain after classic hydrologic units are delineated. Some examples include "true", "classic", "composite", and "remnant" hydrologic units. C - "Closed Basin" hydrologic unit - A drainage area that is 100% non-contributing. This means all surface flow is internal, no overland flow leaves the hydrologic unit through the outlet point. F - "Frontal" hydrologic unit - Areas along the coastline of lakes, oceans, bays, etc. that have more than one outlet. These HU's are predominantly land with some water areas at or near the outlet(s). W - "Water" hydrologic unit - Hydrologic units that are predominantly water with adjacent land areas, ex. lake, easturies, harbors. I - "Island" hydrologic unit - A hydrologic unit that is one or more islands and adjacent water out to the toe of the shore face. U - "Unclassified" hydrologic unit - A hydrologic unit that can't be defined or doesn't fit into one of the types that have been listed. Hu_12_ds: Sixth Level Downstream Hydrologic Unit Code - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) Populate this field with the 12-digit code of the 6th level hydrologic unit that is receiving the majority of the flow from the subwatershed. Outlets created by ditching or other artificial drainage are not to be considered for this field. If a HU flows into an ocean or the Gulf of Mexico populate this field with "OCEAN" and if a HU flows into one of the Great Lakes use the term "LAKE". If a HU flows across international borders use "CANADA" or "MEXICO" depending on which country the HU drains into. If an HU is a closed basin, then populate this record with the term "CLOSED BASIN". Hu_12_name: Sixth Level Hydrologic Unit Name - (FIELD REQUIRED, ATTRIBUTES OPTIONAL) This field is for officially recognized names only. Populate this field by following the directions in subsection 6.3 "Watershed and Subwatershed Naming Protocol". The name used to attribute the subwatershed should be used only once within a 6th level unit. Some 10-digit HU were assigned the huc_12 number when no GNIS name was identified on the DRG-Es. Hu_12_mod: Sixth Level Hydrologic Unit Modifications - (REQUIRED) This field should identify any type of modifications to natural overland flow that alters the location of the hydrologic unit boundary for a 12-digit subwatershed. In the attribute field, identify from most significant to least significant modification(s). Use one or more of the following abbreviations in uppercase to identify your modification(s). If using more than one abbreviation, separate with a comma with no space after the comma. SC - Stormwater Canal ID - Irrigation Ditch IT - Interbasin Transfer BC - Barge Canal SD - Stormwater Ditch PD - Pipe Diversion CD - Channel Diversion NC - Non-Contributing KA - Karst LE - Levee NM - No Modifications OC - Overflow Channel DM - Dam at outlet or HU boundary OT - Other Hu_12_type: Sixth Level Hydrologic Unit Type - (REQUIRED) Populate this field with the hydrologic unit type from the list provided that most closely identifies the subwatershed. Use any of the one digit abbreviations in uppercase that is provided in the list. S - "Standard" hydrologic unit - Any land HU with drainage flowing to a single outlet point, excluding non-contributing areas. This includes areas or small triangular wedges between adjacent HU's that remain after classic hydrologic units are delineated. Some examples include "true", "classic", "composite", and "remnant" hydrologic units. C - "Closed Basin" hydrologic unit - A drainage area that is 100% non-contributing. This means all surface flow is internal, no overland flow leaves the hydrologic unit through the outlet point. F - "Frontal" hydrologic unit - Areas along the coastline of lakes, oceans, bays, etc. that have more than one outlet. These HU's are predominantly land with some water at or near the outlet(s). W - "Water" hydrologic unit - Hydrologic units that are predominantly water with adjacent land areas, ex. lake, easturies. I - "Island" hydrologic unit - A hydrologic unit that is one or more islands and adjacent water out to the toe of the shore face. U - "Unclassified" hydrologic unit - A hydrologic unit that can't be defined or doesn't fit into one of the types that have been listed. ArcInfo (.pat) and ArcView Polygon Format Item name Width Output Type (ArcView) N.Dec. Example Huc_8 8 8 C - 01080201 Huc_10 10 10 C - 0108020103 Huc_12 12 12 C - 010802010310 Acres 8 12 F N 0 026739 States 11 11 C - KS,MO,OK Ncontrb_a 8 12 F N 0 357 Hu_10_ds 10 10 C - 1710020504 Hu_10_name 80 80 C - Upper Blue River Hu_10_mod 20 20 C - CB,NC,ID Hu_10_type 1 1 C - S Hu_12_ds 12 12 C - 171002050402 Hu_12_name 80 80 C - Drift Creek-Big Bear River Hu_12_mod 20 20 C - SD,KA,PD Hu_12_type 1 1 C - C 2) .aat attributes Hu_level: Hydrologic Unit Level - (REQUIRED) This field provides the means to create cartographically pleasing maps. Populate this field with the highest hydrologic unit level (smallest number) for the line (arc) represented by the record. Record the level using numbers 1 through 6 representing each level with 1 being the highest and 6 the lowest level. An example would be if a line represents a region, subregion, basin, subbasin, watershed, and subwatershed boundary, then this cell would be populated with a 1 (Region). Example two would be if a line is a subbasin, watershed, and subwatershed boundary, then the cell would get a 4 (Subbasin). Use one of the levels provided in the list below. Level Digit# Name 1 2 Region 2 4 Subregion 3 6 Basin 4 8 Subbasin 5 10 Watershed 6 12 Subwatershed Linesource: Line Spatial Data Source - (REQUIRED) The Linesource should indicate the base map source(s) used to delineate at 1:24,000 scale. Populate the field using one of the standardized code(s) listed below in uppercase. If using more than one code, separate with a comma with no space after the comma. TOPO24 - Delineation from hardcopy 1:24,000 scale topographic maps TOPO25 - Delineation from hardcopy 1:25,000 topgraphic maps, only Alaska and Caribbean TOPO63 - Delineation from hardcopy 1:63,360 topographic maps, only Alaska and Caribbean DRG24 - Delineation from 1:24,000 scale Digital Raster Graphics DRG25 - Delineation from 1:25,000 Digital Raster Graphics, only Alaska and Caribbean DRG63 - Delineation from 1:63,360 Digital Raster Graphics, only Alaska and Caribbean DEM10 - Derived from 10 meter Digital Elevation Model DEM30 - Derived from 30 meter Digital Elevation Model NED30 - Derived from 30 meter National Elevation Dateset Model EDNA30 - (formally NED-H), derived from 30 meter Elevation Derivatives for National Applications BATH"scale" (ex. BATH24) - Interpreted from NOAA 1:24,000 scale bathymetric data HYPSO"scale" (ex. HYPSO24)- Delineated from 1:24,000 scale contour data ORTHO"scale" (ex. ORTHO12) - Interpreted from 1:12,000 scale Ortho-imagery DEDEM10 - Drainage enforced 10 meter Digital Elevation Model DEDEM30 - Drainage enforced 30 meter Digital Elevation Model GPS - Derived from Global Positioning System LIDAR - Derived from LIDAR IFSAR - Derived from IFSAR data OTH - Other UNK - Unknown All other reference and source maps not listed should be noted in the metadata. Meta_id: Metadata ID Number - (REQUIRED) Metadata ID is a code that identifies which metadata file applies to the arc. In many cases there will only be one metadata file. However, in some cases more than one metadata file may be created to identify different groups and/or procedures used to produce the lines. These separate metadata files may be identified for each separate arc. The metadata ID should be a 4-character code starting with the 2-letter state postal code, followed by a 2-digit sequence number. For example "OK01", "ID02", etc. ArcInfo Line (.aat) Attribute Format Item name Width Output Type N.Dec. Example Hu_level 1 1 I - 6 Linesource 20 20 C - DEM30,DRG24,GPS Meta_id 4 4 C - OK01
Federal Geographic Data Committee. 2001. Federal Standards for Delineation of Hydrologic Unit Boundaries. June 12, 2001 Draft with emailed amendments to certain polygon and arc attribute structure.
344 Merrow Road
The Watershed and Subwatershed hydrologic unit boundaries provide a uniquely identified and uniform method of subdividing large drainage areas. These smaller sized hydrologic units (up to 250,000 acres) are useful in many programs supported by the Natural Resources Conservation Service and others.
map delineation
Map delineation on paper topographic quads.
Map digitizing
Digitizing begins on NRCS Subwatersheds layer
Data layer attribution, editing, review by CT NRCS and DEP personnel, USGS
Delineation of New York hydrologic unit boundaries for units that cross border
Edge match with Massachusetts: both arcs and attributes
Edge match with available New York data (watershed level only), including digitizing of new hydrologic unit boundaries where necessary to complete all polygons which straddle state border.
Edge match with Rhode Island: both arcs and attributes
Review and editing/combining of smaller subwatersheds to better meet National Standard
Attribute edits to update layer to newest Hydrologic Unit Digitizing Standard
Metadata creation
Reprojection to UTM NAD83
Submission for National Review and Certification
Conversion to Connecticut State Plane Coordinate System - Using ArcGIS 9.1 software, the polygon feature shapefile component to the Watershed Boundary Dataset for Connecticut (ct_hu12_geo83.shp) obtained from the NRCS ftp site was projected from geographic coordinates to the Connecticut State Plane Coordinate System of 1983 (NAD83) and named Watershed_Boundary_Dataset_Poly.shp. Where necessary, excluded the AREA and PERIMETER attributes from both the Shapefile and Attribute Entity portion of the metadata because these attributes are only maintained by ArcInfo software with data in ArcInfo Coverage format. Also deleted line and node feature attribute definitions from the metadata prepared by NRCS because they do not describe polygon features. For cartographic purposes, made an ArcView 3 Legend file and ArcMap Layer file.
Polygon identifiers are visually checked with the DRG backdrop and compared with other available information, such as tables of basins with their codes.
The accuracy of these maps is generally based on the contour information of corresponding DRGs. The differences in positional accuracy between the hydrologic unit boundaries and their digitized map locations is unknown. Hydrologic unit boundaries generally were digitized within 0.01 inches of their locations on the digitizing source. Edge match locations are exact because the data were extracted from a New England-based hydrologic units layer which had been electronically edge-matched.
Subwatershed and Watershed naming conventions differ from the newest standard specifications by being more descriptive of the stream reach which the hydrologic unit encompasses. This was done to minimize confusion in areas where tributary stream names are similar. Other attributes have been added to further clarify location within New England. Subwatershed boundaries were delineated outside the state border in order to complete hydrologic units which straddled the border.
Certain node/geometry and topology (GT) polygon/chain relationships are collected or generated to satisfy topological requirements. (The GT-polygon corresponds to a hydrologic unit or a portion of a hydrologic unit at the edge of a quadrangle sheet.) Some of these requirements include: chains must begin and end at nodes, left and right GT-polygons are defined for each chain element and are consistent throughout. The tests of logical consistency are performed using vendor software. All internal polygons are tested for closure with vendor software. All data are checked for common boundary lines (i.e., adjacent polygons with the same label).
The U.S. Department of Agriculture, Natural Resources Conservation Service, should be acknowledged as the data source in products derived from these data. This data set is to be used as a primary reference source. This is public information and may be interpreted by organizations, agencies, units of government, or others based on needs; however, they are responsible for the appropriate application. Federal, State, or local regulatory bodies are not to reassign to the Natural Resources Conservation Service any authority for the decisions they make. Photographic or digital enlargement of these maps to scales greater than that at which they were originally delineated can cause misrepresentation of the data. If enlarged, the maps will not include the fine detail that would be appropriate for mapping at the small scale. Digital data files are periodically updated. Files are dated, and users are responsible for obtaining the latest version of the data.
P.O. Box 6567
Although these data have been processed successfully on a computer system at the U.S. Department of Agriculture, no warranty expressed or implied is made by the agency regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. The U.S. Department of Agriculture will warrant the delivery of this product in computer readable format, and will offer appropriate adjustment of credit when the product is determined unreadable by correctly adjusted computer input peripherals, or when the physical medium is delivered in damaged condition. Request for adjustment of credit must be made within 90 days from the date of this shipment from the ordering site. Neither the U.S. Department of Agriculture, nor any of its agencies are liable for misuse of the data, nor is it liable for damage, transmission of viruses, or computer contamination through the distribution of these data sets. The United States Department of Agriculture (USDA) prohibits discrimination in its programs on the basis of race, color, national origin, sex, religion, age, disability, political beliefs and marital or familial status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audio tape, etc.) should contact the USDA Office of Communications at (202) 720-5881 (voice) or (202) 720-7808 (TDD). To file a complaint, write the Secretary of Agriculture, U.S. Department of Agriculture, Washington, D.C. 20250, or call (202) 720-7327 (voice) or (202) 720-4107 (TDD). USDA is an equal opportunity employer.
| Data format: | spatial and keys in format Arc Interchange File non-compressed Size: 3.423 |
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| Network links: | http://www.lighthouse.nrcs.usda.gov/gateway/gatewayhome.html |
| Media you can order: | 8 mm cartridge tape(Density 2.3gigabytes) (format tar) 1/4-inch cartridge tape(Density 150megabytes) (format tar) |
Call or write to organization listed under Distributor. Spatial line data are in DLG-3 optional format. Digital line graph files contain area records. A conversion legend is provided for each digital line graph file. Hydrologic unit codes and information concerning the hydrologic unit area are available in a companion ASCII attribute file.
344 Merrow Road