THE NATIONAL INVENTORY OF DAMS
NID website: nid.usace.army.mil
Records for 2016: 90,580

The National Inventory of Dams (NID) is a database of all dams in the United States that meet one of the following criteria: 
1) High hazard classification - loss of one human life is likely if the dam fails, 
2) Significant hazard classification - possible loss of human life and likely significant property or environmental destruction, 
3) Equal or exceed 25 feet in height and exceed 15 acre-feet in storage, 
4) Equal or exceed 50 acre-feet storage and exceed 6 feet in height.

The data is maintained by the U.S. Army Corps of Engineers (USACE), which gathers reports from state and federal regulators into one database that tracks the location, owner, current condition, hazard rating, and overall specs of the dam. Not all of this information is released to the public, unfortunately. The USACE withholds the dam's current condition and hazard rating, as well as the nearest city. Each dam has a unique identifier (NIDID), although a single dam can have multiple structures (and therefore multiple records) with the same NIDID. In these cases, there is a secondary identifier for each separate structure in the field "other_structure_id".

Since that information was available in the last version that NICAR received from the agency (for 2002), we've included that data as a reference point.

BE CAREFUL: hazard rankings for dams can change over time, so the 2002 hazard ranking may not be accurate. Also, the USACE tells us that while NIDID (the unique identifier for dams) should not be reused, there's no guarantee that states do not take NIDIDs from decommissioned dams and reuse them for new dams. The USACE also warned us that some federal dams used the wrong NIDID in previous versions of the data, so they changed. These are all the reasons that NICAR has not joined the two datasets together, and you should be careful when crossreferencing dams in the old data. Make sure to look at the name and location information in both years of data to be sure you have a match.

Be aware of the date that each record was submitted to the USACE (field "submit_date"). Check with state and federal regulators to see if any inspections or other changes at specific dams have taken place since then. 

If questions arise concerning specific dams, the Corps recommends reaching out to the relevant state dam safety office. To find state contacts at the Association of State Dam Safety Officials, go to this website:  http://www.damsafety.org/map/

NICAR also has NID data prior to 2002, going back to 1993. Contact us if you're interested in these older versions of the NID.

The USACE claims to release an update of the data every two years; as of February 2017, the 2016 data is the most current data available. This data was scraped from the NID website in October 2016, the last time USACE updated the data.

NEW IN THE 2016 DATA:

The NID now contains two fields that were not in the 2013 data: city (nearest city to dam) and distance (to nearest city) were previously restricted.

FILES AND FOLDERS INCLUDED IN NICAR .ZIP FILE:

-- dams2016.csv : the main data table for dams from 2016 containing 90,580 records.

—- Dams_Readme.txt: the readme file you’re reading right now.

-- dams_layout.xls : the record layout for the dams2016 table, including data type, description, and relevant codes.

-- import_guide.txt : instructions for importing the data files into Microsoft Access, SQLite and MySQL. 

-- Hazard_by_state.xls : although the ACE doesn't release hazard ratings for individual dams, they do provide aggregate numbers by state on their website, which we pulled into a spreadsheet

-- Finding the Story -- Dams : a guide for journalists that describes the data, flags import fields and discusses how to look for stories in the data

-- Agency Documentation
	NID_DataDictionary2013.pdf : the official record layout from the ACE, which includes descriptions of withheld fields (This was the most recent 	dictionary available online and matches all fields.)
	NIDoverview27Oct2016.pdf : contains some background information about the NID and statistics from the 2016 data (prepared by the USACE)

—- 2013
	dams2013.csv : the main data table for dams from 2013 containing 87,359 records.
	dams_layout_2013.xlsx: the record layout for the dams2013 table, including data type, description and relevant codes
	Hazard_by_state_2013.xlsx: although the ACE doesn’t release hazard ratings for individual dams, they do provide aggregate numbers by state on 	their website, which we pulled into a spreadsheet.
	impot_guide_2013.txt: instructions for importing the data files into Microsoft Access, SQLite and MySQL.
	NIDoverview26May2015.pdf : contains some background information about the NID and statistics from the 2013 data (prepared by the USACE)

-- 2002
	dams2002.csv : the main data table for dams from 2002 containing 79,777 records
	DataDict02.doc : the record layout for the 2002 data, describing each field

NOTES ON USACE's AUTHORITY TO GATHER THE DATA (from the NID website): 
"Congress first authorized the U.S. Army Corps of Engineers to inventory dams in the United States with the National Dam Inspection Act (Public Law 92-367) of 1972. The NID was first published in 1975, with a few updates as resources permitted over the next ten years. The Water Resources Development Act of 1986 (P.L. 99-662) authorized the Corps to maintain and periodically publish an updated NID, with re-authorization and a dedicated funding source provided under the Water Resources Development Act of 1996 (P.L. 104-3). The Corps also began close collaboration with the Federal Emergency Management Agency (FEMA) and state regulatory offices to obtain more accurate and complete information. The National Dam Safety and Security Act of 2002 (P.L. 107-310) and the Dam Safety Act of 2006 reauthorized the National Dam Safety Program and included the maintenance and update of the NID by the Corps. Most recently, the NID was reauthorized as part of the Water Resources Reform and Development Act of 2014.
...
The goal of the NID is to include all dams in the United States that meet these criteria, yet in reality, is limited to information that can be gathered and properly interpreted with the given funding. The NID initially consisted of approximately 45,000 dams, which were gathered from extensive record searches and some feature extraction from aerial imagery. Since continued and methodical updates have been conducted, data collection has been focused on the most reliable data sources, which are the many federal and state government dam construction and regulation offices. In most cases, dams within the NID criteria are regulated (construction permit, inspection, and/or enforcement) by federal or state agencies, who have basic information on the dams within their jurisdiction. Therein lies the biggest challenge, and most of the effort to maintain the NID; periodic collection of dam characteristics from 49 states (Alabama currently has no dam safety legislation or formal dam safety program), Puerto Rico, and 18 federal offices. The Corps resolves duplicative and conflicting data from the 68 data sources, which helps obtain the more complete, accurate, and updated NID. The NID is published every two years."


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