Major Dams of the United States

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   National Atlas of the United States, 200603, Major Dams of the United States: National Atlas of the United States, Reston, VA.

   Online Links:

   • <http://nationalatlas.gov/atlasftp.html?openChapters=chpwater#chpwater>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -163

   East_Bounding_Coordinate: -66

   North_Bounding_Coordinate: 69

   South_Bounding_Coordinate: 18

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: Feb-2002

   Ending_Date: Dec-2004

   Currentness_Reference: Dates of source material

5. What is the general form of this data set?

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference:

      U.S. Department of Commerce, 1987, Codes for the Identification of the States, the District of Columbia and the Outlying Areas of the United States, and Associated Areas (FIPS 5-2): Washington, DC, National Institute of Standards and Technology.

      U.S. Department of Commerce, 1990, Counties and Equivalent Entities of the United States, Its Possessions, and Associated Areas (FIPS 6-4): Washington, DC, National Institute of Standards and Technology.

      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (8121)

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000278. Longitudes are given to the nearest 0.000278. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS1980.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222.
      

7. How does the data set describe geographic features?

   Dam

   Any artificial barrier, including appurtenant works, which impounds or diverts water, and which (1) is twenty-five feet or more in height from the natural bed of the stream or watercourse measured at the downstream toe of the barrier, or from the lowest elevation of the outside limit of the barrier, if it is not across a stream channel or watercourse, to the maximum water storage elevation or (2) has an impounding capacity at maximum water storage elevation of fifty acre-feet or more. This Act does not apply to any such barrier which is not in excess of six feet in height, regardless of storage capacity or which has a storage capacity at maximum water storage elevation not in excess of fifteen acre-feet, regardless of height, unless such barrier, due to its location or other physical characteristic, is likely to pose a significant threat to human life or property in the event of its failure. (Source: Dam Safety Act of 1972 (P.L. 92-367) and Dam Safety Act of 1986 (P.L. 99-662))

   Shape

   The representation of the entity in the data. (Source: National Atlas of the United States)

   Value	Definition
   Point	0-dimensional element

   Dams00x020

   Internal feature number. (Source: National Atlas of the United States)

   Range of values
   Minimum:	1
   Maximum:	8121

   Dam_name

   The official name of the dam. For dams that do not have an official name, the popular name is used. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   <blank>	The name of the dam is not provided in the National Inventory of Dams.

   There is no predefined set of valid dam names. The attribute contains the official name of the dam, or the popular name if there is no official name.

   Other_name

   The reservoir name or names in common use other than the official name of the dam. Names are separated with semicolons. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   <blank>	There are no other names for the dam, or the other names are unknown.

   There is no predefined set of reservoir or common use names.

   Nidid

   The official National Inventory of Dams identification number for the dam, known formerly as the National Id. The first two characters of the identity are the State two letter abbreviation, based on the location of the dam. The last five characters of the identity are a unique number (AB#####). (Source: U.S. Army Corps of Engineers)

   Range of values
   Minimum:	AK00001
   Maximum:	WY83004

   Longitude

   Dam longitude as a single value, in decimal degrees. (Source: U.S. Army Corps of Engineers)

   Range of values
   Minimum:	-162.87781
   Maximum:	-66.015000

   Latitude

   Dam latitude as a single value, in decimal degrees. (Source: U.S. Army Corps of Engineers)

   Range of values
   Minimum:	18.017300
   Maximum:	68.069400

   County

   The name of the county in which the dam is located. If the dam falls in more than one county, the names may be separated by a slash, a comma, or a semicolon. (Source: National Atlas of the United States)

   Value	Definition
   <blank>	The name of the county is not provided in the National Inventory of Dams.

   Formal codeset
   Codeset Name:	Counties and Equivalent Areas of the United States, Its Possessions, and Associated Areas, FIPS PUB 6-4.
   Codeset Source:	U.S. Department of Commerce

   River

   The official name of the river or stream on which the dam is built. If the stream is unnamed, it is identified as a tributary ("TR") to a named river. If the dam is located offstream, the name of the river or stream is entered plus "-OS" or "OFFSTREAM". (Source: U.S. Army Corps of Engineers)

   Value	Definition
   <blank>	The name of the river is not provided in the National Inventory of Dams.

   There is no predefined set of valid river or stream names.

   City

   The name of the nearest city, town, or village that is most likely to be affected by floods resulting from the failure of the dam. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   <blank>	The name of the city is not provided in the National Inventory of Dams.

   There is no predefined set of valid city names.

   Own_name

   The name of the owner of the dam. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   <blank>	The name of the owner is not provided in the National Inventory of Dams.

   There is no predefined set of valid owner names.

   Own_type

   A term indicating owner type. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   <blank>	The owner type is unknown.
   F	The dam is owned by a Federal agency.
   L	The dam is owned by a County, City, Regional, or other similar local government or government agency.
   P	The dam is owned by an individual or individuals, or by a private company.
   S	The dam is owned by a State or by a State agency.
   U	The dam is owned by a public utility.

   Dam_type

   A code or codes indicating the dam type, in order of importance. Codes are concatenated if the dam is a combination of several types. For example, CNCB would indicate a concrete buttress type dam. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   <blank>	The dam type is unknown.
   CB	Buttress
   CN	Concrete
   ER	Rockfill
   MS	Masonry
   MV (or MultiArch)	Multi-arch
   OT	Other
   PG	Gravity
   RE	Earth
   ST	Stone
   TC	Timber crib
   VA	Arch

   Purposes

   A code or codes indicating the purposes for which reservoir is used, in order of importance. The codes are concatenated if the dam has multiple purposes. For example, SCR would indicate the primary purposes of Water Supply and Flood Control and Storm Water Management, followed by Recreation. The data may contain words or abbreviations that were used instead of the appropriate codes; these have been retained. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   <blank>	The purpose of the dam is not provided in the National Inventory of Dams.
   C	Flood control and storm water management
   D	Debris control
   F	Fish and wildlife pond
   H	Hydroelectric
   I	Irrigation
   N	Navigation
   O	Other
   P	Fire protection, stock, or small farm pond
   R	Recreation
   S	Water supply
   T	Tailings

   Yr_compl

   The year when the main dam structure was completed. A value of 0 indicates that the year is unknown. (Source: U.S. Army Corps of Engineers)

   Range of values
   Minimum:	1800
   Maximum:	2003

   Nid_height

   The maximum of either the dam height (the vertical distance between the lowest point on the crest of the dam and the lowest point in the original streambed), the hydraulic height (the vertical distance between the maximum designed water level and the lowest point in the original streambed), or the structural height (the vertical distance between the lowest point of the excavated foundation and the top of the dam) of the dam. The height is given in feet, to the nearest foot. (Source: National Atlas of the United States)

   Value	Definition
   0.00000000000	The height is unknown.

   Range of values
   Minimum:	3.000000000000
   Maximum:	770.00000000000

   Max_stor

   The maximum storage in acre-feet. Maximum storage is the total storage space in a reservoir below the maximum attainable water surface elevation, including any surcharge storage. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   0.00000000000	The maximum storage is unknown.

   Range of values
   Minimum:	1.00000000000
   Maximum:	9700000000.00000000

   Normal_sto

   The normal storage in acre-feet. Normal storage is the total storage space in a reservoir below the normal retention level, including dead and inactive storage and excluding any flood control surcharge storage. A value of 0 may indicate that the normal storage is unknown or may indicate that the dam is normally dry. (Source: U.S. Army Corps of Engineers)

   Range of values
   Minimum:	0.00000000000
   Maximum:	9700000000.00000000

   Surf_area

   The surface area, in acres, of the impoundment at its normal retention level. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   0.00000000000	The surface area is unknown.

   Range of values
   Minimum:	0.01000000000
   Maximum:	20358400.0000000000

   Drain_area

   The drainage area of the dam in square miles. It is defined as the area that drains to a particular point (in this case, the dam) on a river or stream. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   0.00000000000	The drainage area is unknown.

   Range of values
   Minimum:	0.00156250000
   Maximum:	1250000.00000000000

   Hazard

   A term indicating the potential hazard to the downstream area resulting from failure or mis-operation of the dam or facilities. (Source: U.S. Army Corps of Engineers)

   Value	Definition
   L	The potential hazard is low. A dam where failure or misoperation results in no probable loss of human life and low economic and/or environmental loss. Losses are principally limited to the owner's property.
   S	The potential hazard is significant. A dam where failure or misoperation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. These dams are often located in predominantly rural or agricultural areas but could be located in areas with population and significant infrastructure.
   H	The potential hazard is high. A dam where failure or misoperation will probably cause loss of human life.
   U	The potential hazard is unknown.

   State

   The two letter abbreviation for the State in which the dam is located. (Source: U.S. Army Corps of Engineers)

   Formal codeset
   Codeset Name:	Codes for the Identification of the States, the District of Columbia and the Outlying Areas of the United States, and Associated Areas, FIPS PUB 5-2.
   Codeset Source:	U.S. Department of Commerce

   Symbol

   A code indicating how the dam is symbolized in the National Atlas Map Maker. The symbol is determined from the primary Purpose code given for the dam, which is the first or only code listed under the attribute Purpose. Where the Purpose attribute contains a word or abbreviation instead of the appropriate code, the first letter of the Purpose value was still used to determine the symbol code. In these cases the symbol may not accurately represent the true primary purpose of the dam. (Source: National Atlas of the United States)

   Value	Definition
   <blank>	The dam has an unknown purpose.
   C	The dam is for flood control and storm water management.
   D	The dam is for debris control.
   F	The dam contains a fish and wildlife pond.
   H	The dam is for hydroelectric power.
   I	The reservoir contained by the dam is for irrigation.
   N	The dam is for navigation.
   O	The dam or reservoir contained by the dam has a primary purpose other than flood control and storm water management; debris control; fish and wildlife pond; hydroelectric; irrigation; navigation; fire protection, stock, or small farm pond; recreation; water supply; or tailings
   P	The dam contains a fire protection, stock, or small farm pond
   R	The reservoir contained by the dam is for recreation.
   S	The reservoir contained by the dam is for water supply.
   T	The dam contains a tailings pond.

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • National Atlas of the United States

2. Who also contributed to the data set?

3. To whom should users address questions about the data?
   Peg Rawson
   National Atlas of the United States
   12201 Sunrise Valley Drive
   Reston, VA 20192
   

   703-648-4183 (voice)
   [email protected]
   

Why was the data set created?

These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the National Atlas of the United States in the use of these data.

How was the data set created?

1. From what previous works were the data drawn?

   NID (source 1 of 2)

   U.S. Army Corps of Engineers in cooperation with FEMA's National Dam Safety Program, 20050209, National Inventory of Dams, Water Control Infrastructure: U.S. Army Corps of Engineers, Alexandria, VA.

   Online Links:

   • <http://crunch.tec.army.mil/nid/webpages/nid.cfm>

   Type_of_Source_Media: Online

   Source_Contribution: Spatial and attribute information

   Atlas-Cnty (source 2 of 2)

   National Atlas of the United States, 200506, County Boundaries of the United States, 2001: National Atlas of the United States, Reston, VA.

   Online Links:

   • <http://nationalatlas.gov/atlasftp.html?openChapters=chpbound#chpbound>

   Type_of_Source_Media: Online

   Source_Contribution: Attribute information

2. How were the data generated, processed, and modified?

   Date: Dec-2005 (process 1 of 2)

   The full National Inventory of Dams (NID) was downloaded from the NID web site in shapefile format and loaded into ArcView. Using an ArcView query, major dams were selected and placed in a new shapefile. Major dams were defined as dams with a height of 50 feet or more, or with a normal storage capacity of 5,000 acre-feet or more, or with a maximum storage capacity of 25,000 acre-feet or more. (The International Committee on Large Dams considers dams over 50 feet to be large dams. The USGS Water Resources Division considers large reservoirs to be those with a normal storage capacity of 5,000 acre-feet or more, or with a maximum storage capacity of 25,000 acre-feet or more.)

   One dam in Guam and one dam in the Trust Territories were deleted. Eighty-nine dams without valid latitude/longitude coordinates were also deleted.

   Because the text fields contained entries in a mix of formats, some in all capitals and some in capitals and lower-case, all text entries were changed to all capitals.

   Some dams were missing county attribute values. The appropriate values were determined by comparing the dam locations to the Atlas-Cnty file. One dam was deleted because it was described as being in Maryland but had coordinates that placed it in Virginia.

   Invalid values for owner type (197 records), dam type (10 records), and year completed (3 records) were changed to blanks to indicate that the values are unknown. The attribute Purposes contained some invalid codes; these were removed but valid codes and duplicate codes were retained. Thirty-nine records contained a value of -9.9 for Nid_height. The appropriate value for each record was determined by looking at the dam height, structural height, and hydraulic height values in the source data. One invalid value for hazard was changed to U to indicate that the hazard potential is unknown.

   The shape file was converted to an ArcInfo coverage and then converted to NAD 83 for display purposes. The result was then converted back to shapefile format.

   Data sources used in this process:

   • NID05
   • Atlas-Cnty

   Date: 20-Mar-2006 (process 2 of 2)

   An attribute was added to the shapefile to allow for symbolization in the National Atlas Map Maker.

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?

2. How accurate are the geographic locations?

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

   This file contains those dams from the National Inventory of Dams with a height of 50 feet or more, or with a normal storage capacity of 5000 acre- feet or more, or with a maximum storage capacity of 25,000 acre-feet or more. Dams outside of the 50 States, Puerto Rico, and the U.S. Virgin Islands are not included, nor are dams for which there is no positional information in the National Inventory of Dams.

5. How consistent are the relationships among the observations, including topology?

   None

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None

Use_Constraints:

None. Acknowledgment of the National Atlas of the United States of America would be appreciated in products derived from these data.

1. Who distributes the data set? (Distributor 1 of 1)
   Earth Science Information Center, U.S. Geological Survey
   507 National Center
   Reston, VA 20192
   

   1-888-ASK-USGS (1-888-275-8747) (voice)
   

   Contact_Instructions:

   In addition to the address above there are other ESIC offices throughout the country. A full list of these offices is at <http://ask.usgs.gov/esic_index.html>.

2. What's the catalog number I need to order this data set?

3. What legal disclaimers am I supposed to read?

   Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made by the U.S. Geological Survey regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. No responsibility is assumed by the U.S. Geological Survey in the use of these data.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	ESRI Shapefile
     Network links:	<http://nationalatlas.gov/atlasftp.html?openChapters=chpwater#chpwater>

     Data format:	SDTS
     Network links:	<http://nationalatlas.gov/atlasftp.html?openChapters=chpwater#chpwater>

   • Cost to order the data: There is no charge for the map layer.

Who wrote the metadata?

Dates:

Last modified: 21-Mar-2006

Metadata author:

Peg Rawson
National Atlas of the United States
12201 Sunrise Valley Drive
Reston, VA 20192

703-648-4183 (voice)
[email protected]

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)