Making a Splash in Water Management

Water is perhaps the most important of all natural resources. Being critical to life, it is necessary that we keep an eye on this crucial resource to monitor both its quality and quantity so that we can intervene where possible. With the United Nations Environment Programme estimating that 2.5 billion people worldwide could face water scarcity by as soon as next year, this problem is more urgent than ever.

Water quality encompasses various chemical, physical, and biological characteristics that determine its suitability for supporting life. One critical aspect of water quality is the concentration of nutrients, such as nitrate levels, which play a significant role in shaping the ecological dynamics of aquatic environments. Elevated nitrate levels in water can have direct and indirect effects on the health of organisms within the ecosystem. Some species of algae and bacteria thrive in nitrate-rich environments, outcompeting other organisms and disrupting the balance of the food web. Additionally, the consumption of water with high nitrate concentrations can have detrimental effects on the health of fish and other aquatic organisms, potentially leading to reproductive issues and long-term population declines.

It is known that the volume and quality of natural bodies of water is greatly impacted by many factors, including precipitation and changes in temperature. For reasons such as these, monitoring these water sources is very challenging. Taking an occasional snapshot of these measurements could lead to incorrect assumptions about the general state of the water over a longer period of time.

It is with these challenges in mind that a team of researchers at the Pohang University of Science and Technology in Korea have developed an uncrewed surface vehicle that can measure the volume and nitrate concentration of a body of water continuously to show changes over time. This vehicle has been in operation for over a year in a reservoir in South Korea.

A boat-like floating platform was equipped with SonTek's rQPOD remote control surveying package to give it mobility. This package provides the motors and remote control equipment needed for basic operation of the vehicle. To support water quantity measurements, the SonTek HydroSurveyor-M9 Acoustic Doppler Current Profiler, the Power/Communication Module, and the Real Time Kinematic positioning GPS were attached to the boat to capture bathymetric data. This setup is capable of measuring water depths of up to 80 meters, and the onboard GPS can pinpoint the exact location of each depth reading.

As far as water quality is concerned, the vehicle was equipped with a YSI EXO2 multiparameter sonde to collect data. This instrument can collect a measurement every second for water temperature, pH, electro conductivity, dissolved oxygen, and nitrate concentration. These measurements can also be correlated with GPS data for localization, and is logged on-device for later analysis.

Over the course of a one year experiment, the uncrewed vehicle went on 30 excursions to collect measurements. Dramatic differences in nitrate levels, ranging from one to four tons were observed due to seasonal variations. Following an intense episode of rainfall, it was noted that nitrate concentrations were found to be 17% lower. These large fluctuations clearly demonstrate the importance of frequent monitoring of bodies of water. Capturing a single snapshot is likely to grossly under- or overestimate the typical state of the water.

Considering the implications of their work, a member of the research team noted that it “is envisioned that this research will provide a guiding framework for the development of the next generation of the Korean national water resources management system, leveraging advanced technologies like uncrewed aerial vehicles to enhance prediction accuracy and optimize water management.”