A microfluidic analyser platform for a number of key water quality parameters has been developed. The platform utilises colorimetric reagent chemistry for detection and quantification of phosphate, nitrate, pH and chemical oxygen demand (COD). The system integrates microfluidic analytical systems, optical detection systems, and wireless communications into a low-cost, portable device capable of autonomous operation under environmental conditions for extended periods. The platform has been successfully tested and validated under various conditions including deployments in freshwater, estuarine water and municipal wastewater. The system uses the vanadomolybophosphoric acid method for phosphate detection, the chromotropic acid method for nitrate detection, a combination of pH indicators for pH measurement, and a variation of the standard method using dichromate for COD analysis. In each case a colour change is developed after mixing the water sample with a reagent (or combination of reagents) in a microfluidic manifold where mixing and reaction take place. The colour change is detected using a light emitting diode (LED) and photodiode based optical detector, allowing quantification of the target analyte in the original sample. Data is stored on a Flash memory chip and also transmitted to the user via wireless communications. Wireless communication modes such as GSM or ZigBee radio are chosen according to the specific application in question. In this paper we describe the design and operation of the analyser platform and present data from laboratory and field trials of the system.