In this work, algorithms were developed for retrieving water quality parameters related to Singapore's reservoirs. The main constituents that affect the water reflectance (WR) – i.e. proportion of incident light reflected from the surface of water bodies after removing the surface glint component – are the suspended particles, phytoplankton and coloured dissolved organic matter (CDOM). The existing absorption spectrum model for phytoplankton in seawater is not accurate for the phytoplankton types that exist in the fresh water environment. The phytoplankton absorption spectrum was modelled by a series of Gaussian peaks from 400 to 750 nm. The peak strengths were dynamically derived from the WR measured. The phytoplankton absorption model is incorporated into a semi-empirical WR model for retrieving the absorption and backscattering coefficients of water components such as suspended sediments, CDOM and phytoplankton. The chlorophyll-a concentration and water turbidity estimated using this model correlate well with field sampling measurements, with coefficients of determination (R2) exceeding 0.8.