Skip common site navigation and headers
United States Environmental Protection Agency
Great Lakes Monitoring
Begin Hierarchical Links EPA Home > Great Lakes > Monitoring > Data Projects > Great Lakes Environmental Database

Great Lakes Environmental Database

GLENDA Query System
Retrieve data from GLENDA

Reporting Standards
Guidance on specific formats for data submissions

Allowable Codes Tables
Tables of GLENDA-recognized codes

About the Great Lakes Environmental Database

The Great Lakes National Program Office (GLNPO) collects environmental data on a wide variety of constituents in water, biota, sediment, and air.  Long after the studies are completed, the data remain and must be managed. Central to the data management effort is a computerized relational database system to house Lake Michigan Mass Balance and other project results. That system, the Great Lakes Environmental Database (GLENDA), was developed to provide data entry, storage, access and analysis capabilities to meet the needs of mass balance modelers and other potential users of Great Lakes data.

Development of GLENDA began in 1993 with a logical model based on the modernized STORET concept and requirements analysis. This was followed in 1994-1995 with the development of field and laboratory reporting requirements, preliminary reference tables, and the initial creation of the physical tables. Recent years have seen the completion of the physical database and most reference tables, the creation of software tools to access the database, and the creation and use of upload routines to load Lake Michigan Mass Balance data.

Subject Areas
GLENDA was designed to include data from four subject areas: project/organization, station/location, field monitoring activities, and results. 

  • The project/organization subject area includes such information as the name and description of the project, the contract, co-operative agreement or grant that the data were collected under, the organization and persons involved in the project along with their mailing addresses, electronic addresses, and telephone numbers.
  • The station/location subject area includes such information as the name of the sampling station and its description, the latitude and longitude of stations and any offsets or areas, the geopositioning technique and accuracy, and names and codes of counties, states, and similar geographic information.
  • The field monitoring activities subject area includes such information as visits to stations for monitoring, any observations or measurements taken during sampling or in the lab, and any remarks during field sampling or lab activities.
  • The results subject area includes such information as analytical results, analytes, units of measure, correction factors, quality assurance codes and flags, and any remarks on laboratory analyses.
simplified entity-relationship diagram for GLENDA

Table Types
There are three main types of tables in GLENDA based on the type of information they contain: reference, static, and dynamic. 

  • Reference tables primarily include lists of reference-type information such as lists of allowable codes or units that can be referred to by other tables. Examples are laboratory and field remark codes, quality control codes, units of measure, analytes, and so forth. These tables are supplied by GLNPO and are fixed, with additions being rare.
  • Static tables include information about projects, organizations and people, sampling stations and their locations, and so forth. These data are supplied by users or participants on an as-needed basis when a new project is undertaken.
  • Dynamic tables include information on samples and results, including field and laboratory data. These data are supplied by users or participants whenever new sampling and analyses are undertaken.



Begin Site Footer

EPA Home | Privacy and Security Notice | Contact Us