Database Entrance
Selectively extract, tabulate, and download specific subsets of water quality data collected by the USGS. You may create either HTML formatted tables of data or comma delimited ASCII files that can be incorporated into spreadsheets, graphics packages, or statistical applications. If you intend to use any of the data for publication please view the CITATIONS page.
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| There are two different ways to query this database: |
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Easy: Recommended for beginners and others not quite sure what they are getting
into. Provides help and guidance so that you don't create a meaningless
query and/or accidentally crash your browser. All parameters are defined. Splits the process into 3
relatively simple steps. |
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Expert: A single page with all of the query options, with much less help and guidance available
to the user. This is recommended for scientists familiar with the data, as well as database developers and frequently returning surfers. |
In order to use the database properly and understand the limits of the data itself,
please check:
Which YEARS we have data available
STRUCTURAL INFO (which will help you to
obtain the data you want)
DISCLAIMER (so you are not misled)
DATA AVAILABILITY (dates)
CTD and discrete measurements are available from 1969 through present.
Light attenuation data not avialable 2002-2006.
Nutrient data: NO3+2, NH3,
PO4, DSi are available 1969-2007
NO2 data available 1969-2004
NOTE that nutrient data are not collected on all cruises or at all stations, see STRUCTURAL INFO.
Tidal Height Data and Delta Outflow Index are no longer available here, please see the NOAA website and Dayflow website to access those datasets.
STRUCTURAL INFO
Tables
The database is divided into 2 tables containing the CTD and nutrient data respectively.
In general, the CTD and nutrient tables may be considered one source of information. If your query contains both CTD and nutrient data, your results will include all of the CTD data
and any nutrient data collected at the same time/location as CTD data.
Nutrient data were usually collected at a small subset stations of the CTD data collection on any particular date.
On rare occasions, nutrient data were collected at times/locations when CTD data were not collected.
If you wish to view these data, only choose nutrient parameters, do not include CTD data in your query.
Discrete data
Discrete data/water grab samples (chlorophyll a, dissolved oxygen, and SPM) occur at a subset of CTD stations on
any particular cruise. Since 1988, these data are listed at the 2m and bottom depth bins where collected.
Light extinction coefficient is listed on the 1m line. Prior to 1988 when CTD use began, light attenuation is
on the 0.5m line and other discrete parameters were collected at variable depths (commonly 0.5m, 1m, and 2m).
To best inform your query, view the data table (in Data Visualization ) for your respective cruise to determine where data were
collected. On each page of data plots there is a button in the upper right hand corner that links to the data
table.
Database size
The current size of the database is approximately 147,000 rows. Data queries which do not specify appropriate constraints can produce a large (several megabyte) HTML table, which
many browsers have trouble handling. Until you are comfortable using this relational
database and are familiar with the way it outputs data,
use the "Easy" interface.
DISCLAIMER
- Time of day values for cruise data sampled 1981 through 1987 are estimates, and accurate to only within +/- half an hour.
- Nutrient data (NO2, NO3+NO2, NH3, PO4,
Si) acquired after 1995 are preliminary, unpublished, and have not yet been subjected
to our procedures of quality assurance, and therefore should not be quoted or published elsewhere
- Please let us know if you are using our data in ANY publication (email tschraga@usgs.gov)
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U.S. Department of the Interior |
U.S. Geological Survey
