Database Fact Sheet

September 2001

The National Nutrient Database stores and analyzes nutrient water quality data and serves as an information resource for states, tribes, and others in establishing scientifically defensible numeric nutrient criteria. It contains ambient data from our Legacy STOrage and RETrieval (STORET) data system, the US Geological Survey's National Stream Quality Accounting Network (NASQAN) data and National Water Quality Assessment (NAWQA) data, and other relevant sources such as universities and states/tribes. The ultimate use of the data is to derive ecoregional waterbody-specific numeric nutrient criteria. We will also use this database to develop ecoregionally representative nutrient criteria for all waterbodies of the United States.

Background
What is the Nutrient Database?
What are the features of the Nutrient Database?
What kind of data is in the database?
How was the data checked for quality?
What are nutrient criteria?
What is the database used for?
Will this database be modified in the future?
How can I access the database?
How can I get more information?

Background

In June 1998, EPA published the National Strategy for the Development of Regional Nutrient Criteria in the Federal Register. The National Strategy specifically states that the EPA will establish nutrient criteria that reflect the different types of water bodies and different ecoregions of the country. It also says the Agency will help states and tribes adopt numeric water quality standards based on these criteria. EPA developed the National Nutrient Database to derive these data-driven criteria and to store and analyze nutrient data. The database can help states and tribes analyze nutrient data and the EPA criteria.

What is the Nutrient Database?

The nutrient database is a compilation of data from various sources that groups the data by specific waterbody and parameters. States, tribes, and others can use the database to summarize data to derive ecoregional waterbody-specific numeric nutrient criteria that can serve as baseline for establishing scientifically defensible nutrient criteria.

What are the features of the Nutrient Database?

The Oracle database is web-enabled and contains locational information to georeference the data points, station identification used to validate county and ecoregional locations, and analytically-measured values for the nutrient parameters of interest.

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What kind of data is in the database?

The EPA converted legacy STORET data, NASQAN and NAWQA data, and other relevant nutrient data from universities and states/tribes into the National Nutrient Database. The database contains ambient data for waterbodies of the United States, predominantly from freshwater systems.

How was the data checked for quality?

The following quality assurance measures were performed:

Sampled locations were verified.
Duplicate samples were deleted.
Data points collected by or downstream to effluent discharge points were deleted.
Corresponding station IDs, Hydrologic Code Unit (HUC) codes, county, and ecoregions were verified.
States verified that EPA or Standard Methods were used in sampling and analysis of nutrient data.

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What are nutrient criteria?

Nutrient criteria are numerical values for both causal (total phosphorus and total nitrogen) and response (algal biomass/ chlorophyll a, and measures of water clarity, e.g., Secchi depth) variables. We expect these criteria to be used to help identify problem areas, serve as the basis of development for state and tribal water quality criteria for nutrients, and evaluate relative success in reducing cultural eutrophication. EPA is publishing nutrient criteria values as recommendations to states and tribes in setting nutrient water quality standards for waterbodies of the United States. In 2000, EPA published values for seventeen ecoregions (eight for Lakes & Reservoirs, eight for Streams & Rivers, and one for Wetlands). EPA will continue to develop numeric criteria and help states and tribes develop their own nutrient criteria.

What is the database used for?

The nutrient database can be used to compile the national nutrient data. It was used to develop the ecoregional criteria published by the EPA. The database allows states, tribes and stakeholders to replicate EPA's data analysis and to perform their own independent analyses. It also gives states and tribes access to data for refinement of EPA's criteria and helps states and tribes share data within nutrient ecoregions regardless of political boundaries.

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Will this database be modified in the future?

Future versions of the database will allow the user to perform statistical analyses on subsets of data in the database application and to graphically display these analyses using a Web browser.

The nutrient database will also be linked to the EPA's EnviroMapper which will allow users to display station point data by aggregate ecoregion, Level III ecoregion, and by county. Information will also be displayed by year, season, decade, and parameters. Quartile values (e.g., 25th, median, and 75th percentile) will be included for display in the EnviroMapper. Users will be able to zoom in by waterbody name, as listed in the Nutrient Database, to display station points.