An apparatus (1) for real-time, in-situ monitoring of river water quality, is disclosed. The apparatus (1) includes a main cylindrical buoy structure (2) configured to float about a waterline (201), the buoy structure (2) houses a plurality of sensors (106a, 107a, 108a) configured for monitoring of river water quality; an upper instrument housing (3) extending upwards from the buoy structure (2); a plurality of energy harvesting systems (4, 51, 7); a sensor cleaning system (120) disposed within the buoy structure (2), the sensor cleaning system (120) being configured for cleaning of the plurality of sensors (106a, 107a, 108a); and a lower metallic rectangular structure (6) secured to the cylindrical buoy structure (2)