In this study, two segments (WEFA) in the Harbin City reach of the Songhua
River system were considered. For each segment, there were several pollution
sources and these multiple influences led to deterioration of downriver water
quality. A one-dimensional multi-pollution source water quality model (MPSWQM)
was used here to support effective water quality management in the Harbin City
reach of the Songhua River system, with all pollution sources being considered as
point sources. For each WEFAwas usually managed respectively according to certain
water quality goal, the water quality model of this WEFA would be set up solely. The
particular MPSWQM of each segment was established based on the number of
pollution sources in the segment. With the assumption that the flow of a river is
well-mixed vertically and laterally, if the dispersion component is not taken into
account, the one-dimensional water quality model, for each point source, can be
written as (Chapra, 1997)