We propose a new type of sensors suitable for water quality testing and for monitoring water contamination levels in domestic, industrial and environmental applications. The proposed sensing scheme uses Fourier transform cavity-enhanced absorption spectroscopy and novel compact sensing elements based on nanostructured photonic crystal-type optical coatings enabling the sensitive Fourier-domain processing methodology and maximising the absorption path length within the measurement system. The measurement scheme is shown to be suitable for the determination of small changes in the water absorption coefficients at a discrete set of wavelengths in the visible spectral region in response to small concentrations of pollutants with high sensitivity. The proposed sensors are expected to provide real-time information on the water contamination levels, as well as potentially the types of substances dissolved.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.