In recent years citizen science emerged as a promising technology in environmental science and hydrology with the potential to overcome the lack of in-situ measurements and create efficient ecosystems. This paper provides an up-to-date systematic literature review of applications of citizen science technology in water quality monitoring and estimation. A bridge between citizen science and remote sensing will be established to provide a sound framework for comprehensively discussing the various approaches and applications. A scrutinizing of various water quality parameters and associated measurement and estimation methods is provided, delving into various remote sensing systems (microwave and optical systems) and imaging techniques (hyperspectral and hyperspectral methods). A special interest is focused on reviewing existing relevant crowd-sourcing mobile apps such as EyeOnWater, HydroColor, EnviObserver, Sechhi App, Hydro Crowd, and SIMILE-Lake monitoring, detailing their working mechanisms, algorithms, data acquisition processes, used sensors, and measured water quality parameters. Finally, the paper summarizes key knowledge gaps, challenges and promising directions in this research field.