Quality-Assurance Information

• The file QA_FLD.TXT gives a summary of important changes in national network field methods, constituent coverage, and field sample contamination from 1973 to 1995 that may affect the use and interpretation of WQN stream water-quality data.

Changes in Laboratory Methods

• The file QA_LAB.TXT gives a summary of important changes in national network laboratory methods, reporting conventions, and laboratory sample contamination from 1970 to 1995 that may affect the use and interpretation of WQN stream water-quality data.

Water-Quality Technical Memoranda

• A brief summary of the contents of 60 water-quality memoranda is provided in the file QA_MEMOS.TXT. These memoranda describe national network protocols and changes in methods, constituent coverage, and sample contamination that may affect the use and interpretation of WQN stream water-quality data. Many of these memos are cited in QA_FLD.TXT and QA_LAB.TXT with Hypertext links.

• A chronological listing of the 60 water-quality memoranda is provided.

• A chronological listing of the figures and tables for 7 of the water-quality memoranda, which have separate graphical files stored in PostScript and GIF format, is provided. [Hypertext links to these graphics are also provided in the body of these 7 water-quality memoranda, which can be accessed from the above files.]