THE NATIONAL INVENTORY OF DAMS
NID website: nid.usace.army.mil
Records for 2018: 91,468

This data is provided AS-IS and for free from IRE & NICAR. It has been downloaded from the National Inventory of Dams website at https://nid-test.sec.usace.army.mil/. Since 2002, this is the first official update of the data to re-introduce hazard ratings. 

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. 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".

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 2018, 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 March 2019, the 2018 data is the most current data available. 

NEW IN THE 2018 DATA:

The NID now contains three fields that were not part of the 2016 DATA: purposes (a key listing the different reasons the dam was created), hazards (indicating the hazard level of the dam), record id (a count of each of the dams listed in the database)

There were two columns that were identified in the 2016 NID database listed as primary purpose and all purposes. Those two columns were eliminated and was replaced with a column labeled purposes. 

There are five fields that were included in the 2016 DATA (cleaned by NICAR) but were eliminated in the 2018 DATA: state_code_id (state name), primary purpose (the primary purpose of the dam), all_purposes (various purposes of the dam listed in order of importance), zoom to and created date (date and time stamp of when the data was pulled from the website)

FILES AND INCLUDED IN DAMS2018 .ZIP FILE:

-- dams2018.csv : the main data table for dams from 2018 containing 91,468 records.

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

-- dams_layout.xls : the record layout for the dams2018 table, including data type, description, and relevant codes.

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

-- 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

-- NID_DataDictionary_2018.pdf : the official record layout from the ACE, which includes descriptions of fields

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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