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Search criteria and codes

Search criteria are criteria that you enter to select sites of interest. Codes describe data and aid in its interpretation. This page contains links to a comprehensive set of codes used by this site which can be used an an authoritative reference.

Definitive list of USGS parameters

Site Criteria

Site criteria let you find sites of interest. Site criteria pages exist for current conditions, site information, surface water, groundwater and water quality data. Not all criteria listed below can be used for all data categories.

  • Agency code
The agency that is reporting the data. Agency codes are fixed values assigned by the National Water Information System (NWIS). A list of agency codes is available. [ Tab-separated -- saved to file || Tab-separated -- display to screen || HTML ]
  • Altitude
Altitude of the site referenced to the specified Vertical Datum.
  • Altitude accuracy value
Altitude accuracy is mandatory when altitude is entered. Enter the accuracy of the altitude in terms of the possible error in feet. An accuracy of +/- 0.1 foot would be entered as “.1”. Many altitudes are interpolated from the contours on topographic maps; accuracies determined in this way are generally entered as one-half of the contour interval.
  • Aquifer type
Groundwater occurs in aquifers under two different conditions. Where water only partly fills an aquifer, the upper surface is free to rise and decline. These aquifers are referred to as unconfined (or water-table) aquifers. Where water completely fills an aquifer that is overlain by a confining bed, the aquifer is referred to as a confined (or artesian) aquifer. When a confined aquifer is penetrated by a well, the water level in the well will rise above the top of the aquifer (but not necessarily above land surface). Additional information is available.
  • CASRN
CAS Registry Number is a Registered Trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM.
  • Construction date
Date the well was completed.
  • County
The name of the county or county equivalent (parish, borough, etc.) in which the site is located. A list of codes is available. [ Tab-separated -- saved to file || Tab-separated -- display to screen || HTML ]
  • Data type
All USGS data falls into one or more of these categories
Any Data type Matches data for any available options
Current Conditions and Recent Daily Data Current condition data is any data down to the 15 minute interval that has been transmitted in the last 120 days. Recent Daily-Value Data is the average daily value for a site and it is usually for the past year and a half of recorded values.
Surface Water Water flow and levels in streams, lakes and springs.
Water Quality Chemical and physical data for streams, lakes, springs, and wells.
Groundwater Water levels in wells.
  • Drainage area
The area enclosed by a topographic divide from which direct surface runoff from precipitation normally drains by gravity into the stream above that point.
  • File of site numbers
A previously saved file of USGS site identification numbers, in the format: 
USGS 11447650
USGS 394523084582301
The file may be prefixed by the agency code.
  • File of parameter codes
A previously saved file of parameter codes, in the following format: 
01130	Minor and Trace Inorganics	Lithium, water, filtered, micrograms per liter
01131	Minor and Trace Inorganics	Lithium, suspended sediment, recoverable, micrograms per liter
01132	Minor and Trace Inorganics	Lithium, water, unfiltered, recoverable, micrograms per liter
List of parameter code names, and help finding a code.
  • Groundwater site type- subset of Site Type, site types used by groundwater
The code indicating the type of site to which these data apply. The codes and their meanings are available.
  • Hole depth
The total depth to which the hole is drilled, in feet below land surface datum.
Note: Not all groundwater sites have information on Hole Depth. Such sites will not be retrieved using this search criteria.
  • Hydrologic region
The contiguous United States is broken into 18 different major watersheds. Alaska, Hawaii, and Puerto Rico each have a separate watershed. Additional information is available.
  • Hydrologic unit code (HUC)
Hydrologic units are geographic areas representing part or all of a surface drainage basin or distinct hydrologic feature and are delineated on the State Hydrologic Unit Maps. Each hydrologic unit is identified by a unique number (HUC), and a name. Additional information is available.
Note: Not all groundwater sites have been associated with a Hydrologic Unit. Such sites will not be retrieved using this search criteria.
  • (Internal) Site list
A previously saved file of USGS site identification numbers. This option should only appear on displays if the user is inside the USGS network.
  • Latitude-Longitude (Lat-Long) box
When looking at a map, consider a rectangle that encloses the area of interest to you. The maximum latitude and longitude define the upper-left corner, and the minimum latitude and longitude define the lower-right corner of that box. To find the approximate latitude and longitude try the USGS Earth Explorer. For the best results define the smallest practical latitude-longitude box that includes the area of interest; retrievals from unnecessarily large latitude-longitude boxes (1x1 degree, for example) may yield many undesired sites.
Examples
Degrees-
Minutes-
Seconds		Decimal
Degrees
100 59 01 100.91
45 09 34 45.11
  • Local aquifer (by code)
Local aquifers in the USGS water resources data base are identified by a geohydrologic unit code (a three-digit number related to the age of the formation, followed by a 4 or 5 character abbreviation for the geologic unit or aquifer name). Additional information is available. [ Tab-separated -- saved to file || Tab-separated -- display to screen || HTML ]
Note: Not all groundwater sites have been associated with a Local Aquifer. Such sites will not be retrieved using this search criteria.
  • Local aquifer (by name)
Name of the aquifer. Also known as the geohydrologic unit. Additional information is available.
Note: Not all groundwater sites have been associated with a Local Aquifer. Such sites will not be retrieved using this search criteria.
Local aquifer codes and names are fixed values assigned by the National Water Information System (NWIS). A list of aquifer codes and names is available. [ Tab-separated -- saved to file || Tab-separated -- display to screen || HTML ]
  • Multiple site numbers
A list of multiple site numbers separated by carriage returns (generated by pressing the ENTER key on your keyboard) are used to display many sites simultaneously. Each site in the USGS data base has a unique 8 to 15-digit identification number. You can search using an exact match or match using a partial number. To use an exact match you must include all of the digits including any leading zeros (0) that make up the complete site number. A site will not be found if the site number has a leading zero and it is not included in the string tested using an exact match.
Note: The speed of the search using site numbers (and site names) is very fast using exact matches. The next fastest is matching from the beginning. Searches that match any part of the number (or name) are much slower.
  • National aquifer
National aquifers are the principal aquifers or aquifer systems in the United States, defined as regionally extensive aquifers or aquifer systems that have the potential to be used as a source of potable water.
Most of the national aquifers were published on the map sheet Principal Aquifers, part of the National Atlas of the United States of America. A few additional national aquifers were added from descriptions in the Groundwater Atlas of the United States. The aquifer names are regional names, and may not reflect local names used to refer to an aquifer. National aquifers are identified in the USGS water resources database using the codes available here.
Note: Not all groundwater sites can be associated with a National Aquifer. Such sites will not be retrieved using this search criteria.
A list of National aquifer codes and names is available. [ Tab-separated -- saved to file || Tab-separated -- display to screen || HTML ]
  • Number of observations
Number of records found meeting a given criteria.
  • Parameter code/name
5-digit number used in the US Geological Survey computerized data system, National Water Information System (NWIS), to uniquely identify a specific constituent. List of parameter code names, and help finding a code.
  • Parameter groupings
Parameters are grouped into major categories of water-quality data. Each parameter belongs to one group only. Parameter codes associated with each group.
  • Period of record
Period of record for the data selected. You can enter either or both of the first date or end date to restrict search. The search is done against the first and last date of record for the given type of data, not against the actual data values. Thus, if a site has one sample collected on 1910-01-01 and all following samples collected between 1980-01-01 and 1990-01-01, and the search "first date" is 1950-01-01, this site will pass the test since the period of record for the site would be from 1910-01-01 to 1990-01-01. (NOTE: checking data values explicitly, and not using a summary of the data is time consuming and is not supported currently. )
Dates can be entered in any of the following formats:
FORMATEXAMPLE
YYYY-MM-DD 2000-05-12
YYYY-M-D 2000-5-12
M/D/YYYY 5/12/2000
M D YYYY 5 12 2000
YYYYMMDD 20000512
YYYY.M.D 2000.5.12
  • Sample medium type
Medium type refers to the specific environmental medium that was sampled and analyzed. Medium type differs from site type because one site type, such as surface water, could have data for several media, such as water, bottom sediment, fish tissue, and others. For a listing of the medium types look in the [Codes Help Section]
  • Site name/Local number
This is the official name of the site in the database. For well information this can be a district-assigned local number. Do NOT include "river", "lake", "creek" or other hydrological term. Search for "trinity" not "trinity river", or a complete or partial local number. All name searches are NOT case sensitive.
Note: Site name searches are the slowest way to find sites, and take 5 to 10 times longer than searches using the site number. The fastest site name search is matching from the beginning. Searches that match any part of the name are much slower.
  • Site number
Each site in the USGS data base has a unique 8- to 15-digit identification number. Site numbers are assigned based on this logic. You can search using an exact match or match using a partial site number. To use an exact match you must include all of the digits including any leading zeros (0) that make up the complete site number. A site will not be found if the site number has a leading zero and it is not included in the string tested using an exact match.
Note: The speed of the search using site numbers (and site names) is very fast using exact matches. The next fastest is matching from the beginning. Searches that match any part of the number (or name) are much slower.
  • Site number search on graphs
Each site in the USGS data base has a unique 8- to 15-digit identification number. Site numbers are assigned based on this logic.
  • Site type
The hydrologic setting of the site. This is not equivalent to the type of data collected at the site.
[ Tab-separated -- saved to file || Tab-separated -- display to screen || HTML ]
  • State/Territory
The name of the state or territory in which the site is located.
  • USEPA SRS
http://www.epa.gov/srs/
  • Update time
The Update time option provides the ability to select sites that have been updated or have received new/updated data within the specified interval. The available intervals for selection are dependent on the data type being queried. Note: While current-condition sites normally record data onsite every 15 minutes, the stored data are only transmitted to the web hourly.
  • Water quality method codes
Water Quality method codes are associated with one or many parameter codes. The method codes and associated parameters used in NWIS are available. [ Tab-separated -- saved to file || Tab-separated -- display to screen || HTML ]
  • Well depth
The depth of the finished well, in feet below land surface datum.
Note: Not all groundwater sites have information on Well Depth. Such sites will not be retrieved using this search criteria.

Site Inventory Codes

These codes document attributes of sites in the system.

Time Series Codes

  • Data Descriptor (DD)
A 3-digit number usually expressed as two digits that identifies a series of data values for one parameter at one location at a continuous-recording data site. The DD is the basis for selecting data for download or display as a list, table, or graph. Because more than one type of data may be collected or computed, many sites have multiple DDs.

Groundwater Codes

These codes document attributes unique to groundwater sites in the system.

Surface Water Codes

These codes document attributes unique to surface water sites in the system.

Water Quality Codes

These codes document attributes unique to water quality sites in the system.