Sampling frequency for river quality monitoring

Abstract

Sampling frequency for a water quality monitoring network is presented, and for illustrative purposes the criterion is applied to the Massachusetts portion of the Connecticut River basin. The proposed frequency criterion is based upon the assumption that the primary objectives of future river quality monitoring networks are the determination of ambient water quality conditions and an assessment of yearly trends rather than detection of stream or effluent standards violations. The sampling frequency criterion is derived as a function of the random variability of the river flow. The criterion is specifically related to the magnitude of the expected half width of the confidence interval of the mean of the random component of the annual statistic‐mean log river flow. The appropriate sampling intervals (at each sampling station within the river basin) are determined by specifying equality of this confidence interval half width, which insures a uniform reliability of the annual statistic.