HYDRAULIC MIXING AND FREE CHLORINE RESIDUAL IN RESERVOIRS

An extensive sampling study of reservoir water quality was conducted i n Azusa, Calif. Primary emphasis was placed on providing a better unde rstanding of the dynamics of hydraulic mixing and free chlorine residu al concentration distribution in the reservoir. The reservoir approach ed completely mixed behavior with two exceptions: a degree of short-ci rcuiting between the inlet and outlet (which significantly affected th e T-10 time) and the presence of a stagnant zone in the center core of the reservoir where there was less mixing, and thus older water. Thes e results support the assumption of stratification or partitioning in reservoirs. Regular field sampling is recommended to facilitate the ef fective management of distribution system water quality. In particular , interior sampling of reservoirs can provide useful information that could not be inferred otherwise.