Development of Low Cost Extendable Drifter Equipped with Water Quality Sensors for Estuarine Systems

With growth in anthropogenic activities in shallow water estuaries adjacent to urban areas, there is an increasing need for affordable accurate measurements of the flow and key water quality parameters. This is required to ensure pollution is monitored and acceptable water quality is maintained. Traditionally, these measurements are taken at fixed locations while huge cost is associated with monitoring in large coverage area. With recent improvement in the accuracy of GPS systems, satellite tracked free floating drifters can be employed. Here we present the development and application a low cost drifter- (RTFLOW) - capable of monitoring river velocity and water quality parameters. The RTFLOW drifter is equipped with embedded linux computing device, ublox M8T GNSS receiver and antenna that enables single-frequency Real-Time Kinematic (RTK) positioning. The raw GNSS observation data are processed in real-time or post-processing to derive RTK solution with an accuracy of few centimetre to decimetre depending on the environment. The position solution and sensor data are transmitted to a cloud server through cellular network to allow for real-time tracking of the drifter as well as visualization of water quality sensor data from remote office. Currently, the drifter is equipped to measure and transmit geotagged real time observations of Dissolve Oxygen, Conductivity, Temperature, pH and Turbidity. A low cost turbidimetry is achieved with the use of light attenuation sensor calibrated against standard Nephelometric Turbidity Unit. The performance of RTFLOW is evaluated in Currimundi Lake, an Intermittently Closed and Open Lagoon and Lake adjacent to an urban area. The results demonstrated that RTFLOW readily track sources of discharge in the channel. The observation from RTFLOW can further be integrated with hydrological observations and hydrodynamic model to effectively manage estuarine system.