QUALITY ASSURANCE OF U. S. GEOLOGICAL SURVEY WATER-QUALITY FIELD MEASUREMENTS.

Reference samples are submitted semiannually to field analysts for measurement of these parameters with the same techniques and instruments used in the field. Both the personnel and the instruments involved in making the determinations are recorded. When the data are complete, a report defining the quality of the analytical results is prepared and circulated to appropriate District, Regional, and National offices. Field data, in addition to their immediate use, are normally placed in a national data base and are available to all hydrologists. As a result, the quality of field measurements can have a profound effect on their investigations. The quality assurance program described is designed to insure that the field data of the Water Resources Division are highly accurate.