NUMERICAL MODELING FOR THE SELECTION OF EFFLUENT OUTLET LOCATION

Abstract

This paper presents the hydro-environmental sustainability study of a planned mill in the Muan
and Riko River area, Province of East Kalimantan, Indonesia. The study aims to choose the best location among
the three options for the mill’s water effluent outlet in Muan River. The surface-water modeling system is used
to numerically model sedimentation patterns due to the placement location of the water intake and effluent
outlet for the prospective mill. The model inputs are tidal propagation and river discharges from the tributaries.
A field measurement is also carried out to provide solid data for the model construction and validation. The
model shows a good agreement with the field data, with errors below 5%. It is found that the pattern of bed
elevation change is closely affected by the location of the outlet, with a maximum yearly bed change of 1.4 m.
The scenario where the effluent outlet is placed at the upstream of Muan River shows the lowest bed change
along Muan River. However, dredging measures to maintain the river depth are required to make sure that the
river remains accessible for water transportation.