This project is developing a multi-parameter system for the highly sensitive and accurate detection of carbon dioxide in groundwater. The stand-alone system will include novel distributed fiber optic sensors for CO₂, pH, and salinity, as well as a commercially available distributed sensor for temperature. The sensors will be fabricated by coating optical fibers with chemically-sensitive indicator-doped polymers, thus rendering the entire length of the optical fiber a sensor capable of covering large areas in distances of thousands of feet. The project involves developing two novel sensitive claddings for salinity and pH sensing. Once developed, optical cables sensitive to each parameter will be produced. Those cables will be combined with a CO₂ sensitive cladded fiber as well as an off the shelf fiber optic temperature sensor to produce a real time monitoring network to be used for CO₂ storage monitoring, verification, accounting (MVA), and assessment operations, which will be validated in the field.