In Southeast Asia, there is a growing concern for monitoring water quality not just from the standpoint of municipal water management but also from an ecological health perspective. Historically, the biggest challenge in developing biotic indices for tropical systems has been the dearth of information on taxonomic composition and faunal sensitivities to local stressors. This led to the inception of a long term biomonitoring project in Singapore, geared towards collecting comprehensive biological and physico-chemical data from all 17 freshwater reservoirs. A previously developed benthic quality index was recently modified based on the addition of newly acquired benthic invertebrate and water quality data collected from 13 reservoirs in 2011-2013. In total, 68 taxonomic groups were sampled represented by over 243,000 specimens. We employed non-linear generalized additive models to evaluate response curves of each taxonomic group against organic enrichment parameters. This was followed by a weighted average approach to calculate tolerance weights for each taxonomic group resulting in a single index score. A range of indices were derived representing various combinations of organic enrichment parameters, including chlorophyll a, turbidity, dissolved oxygen, phosphorus and nitrogen. Each index was evaluated against the respective environmental driver(s) using a combination of multivariate techniques. Further steps in the analysis will explore relationships between each index and a composite stressor to determine the suitability of the index in reflecting a gradient of organic pollution.