WATER QUALITY AND SEDIMENTATION MODELING IN SINGKARAK LAKE, WESTERN SUMATRA

Abstract

Numerical modeling of the spatial distribution of water quality in Singkarak Lake, Western
Sumatra, Indonesia is conducted. Field measurement data are collected, including bathymetry, water level,
current velocity, and water quality data. The measured parameters in the water quality survey are the total
suspended sediment (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD), dissolved
oxygen (DO) and phosphate (P). The finite element model is implemented using a surface-water modeling
system (SMS). The model includes flow, constituent, and sedimentation models. Validation of the flow model
is achieved by matching the current and the water elevation between the model and the field data. The
validation shows good agreement. The model is aimed at observing yearly water quality and sedimentation
change at the lake. The results from the constituent model show that the Sumpur and Sumani Rivers are having
the greatest effect on the water quality of the lake in its northern and southern regions, respectively. A bed
change of around 30–40 cm per year is found at the inlets of both of these rivers. Overall, the model shows that
the lake water is only suitable for irrigation or fishing hatchery, and not for drinking water, according to the
criteria for water quality standards in the Indonesian government’s Regulation 82 of 2001.