Raw water in impounding reservoirs is a major drinking water source in Hong Kong. The Water Supplies Department (“WSD”) monitors the water quality and collects water samples in impounding reservoirs on a regular basis to keep track of any changes in water quality, so that drinking water safety can be ensured by more effective water treatment processes in water treatment works. To further enhance the water quality monitoring, the WSD has introduced a new Unmanned Surface Vessel (“USV”) system in recent years to perform automatic water quality monitoring and sampling in impounding reservoirs, boosting efficiency through adoption of innovation and technology. This time, I have invited a colleague from the WSD to talk about the details.

Enhancing emergency responsiveness

Currently, there are 17 impounding reservoirs for raw water storage in Hong Kong. The water quality of impounding reservoirs may be sometimes affected by the natural environmental conditions or unexpected incidents. For instance, a change of weather may lead to excessive growth of algae, causing an impact on water quality. The USV “fleet” of the WSD mainly conducts water quality monitoring in the Plover Cove Reservoir (“PCR”) - Hong Kong’s impounding reservoir with largest surface area - to keep track of water quality and facilitate immediate action in case of emergency.

Equipped with water quality monitoring units

Waterworks chemist of the WSD, Mr TANG Ho-wai, says the USV system consists of a base station computer and four electric USVs. Each USV is equipped with a water quality monitoring unit to monitor temperature, conductivity, turbidity, dissolved oxygen, pH, chlorophyll-a and blue green algae. The water sampling unit on each vessel is connected to a pipe underneath, pumping water into the water sampling tank directly. The USVs are also equipped with Global Positioning System receivers and obstacle avoidance system for navigating around obstacles during operation.

Auto-navigation along a pre-set route

Mr TANG Ho-wai tells us that, by using the base station computer, the WSD staff can remotely control the USVs to navigate automatically along a pre-set route, monitor water quality and conduct sampling at designated locations. The water quality data collected can be sent to the base station computer in real time for quick analysis and generation of a surface water quality profile indicating areas with significant variation in water quality for appropriate follow-up.

Endurance for a distance of 11 to 14 km

The four USVs can in a day monitor different parts of the surface of PCR, which is 12 km2 in surface area, and also record the distribution and changes of surface water quality at the impounding reservoir. The vessels are equipped with a battery that can support continuous operation of about 3 to 4 hours, which is about 11 to 14 km if converted into traveling distance. However, according to Mr TANG Ho-wai, the longest hours and distance that a USV can actually operate depend on a number of factors, such as settings of the water quality monitoring work, and the day’s wind direction and speed, etc. Based on routine and USV’s monitoring data, the water quality of the PCR has been consistently steady and satisfactory.

Numerous advantages of USVs

Compared with traditional vessels for water quality monitoring, the USV system has many advantages. For example, USVs can be operated by a trained technician, whereas traditional vessels have to be operated by a licensed vessel operator. USVs are smaller in size and can travel to relatively narrow or shallow areas in impounding reservoirs. Moreover, they can simultaneously cover a number of monitoring points for higher efficiency. They can also generate water quality graphical reports with reference to the topographic map of the impounding reservoirs, making it easier to diagnose the distribution and trends of water quality data. With ease of deployment and transportation, the whole USV system can be deployed to work at various impounding reservoirs in the event of water quality emergencies. Furthermore, USVs of the WSD are powered by renewable energy. The WSD has specially installed a solar panel system outside the USV storage house for generating electricity to operate the USVs.

Extension of the project to other impounding reservoirs

Looking forward, Mr TANG Ho-wai says the WSD plans to use USVs at other impounding reservoirs, such as the High Island Reservoir, to monitor water quality and collect water samples. The department will continue to attempt the upgrading of the intelligence of the system, so that it can work in response to real-time water quality data. For example, when certain areas of an impounding reservoir are found to have a higher chlorophyll reading, USVs will automatically increase the number of monitoring points to collect more data and water samples, so that laboratory staff can conduct a more detailed analysis on the quantity and species of algae later in the laboratory.

Innovation and technology development is the global trend. I am pleased to see creativity and innovation in various departments in recent years. As I have introduced before in “My Blog”, examples include the use of the “robot dog” to enhance slope safety management; the employment of Building Information Modelling (“BIM”) technology to overcome graphical limitations and time-space constraints to improve project planning and design; the adoption of Modular Integrated Construction (“MiC”) method to speed up the building process and enhance safety; the development of the “Common Spatial Data Infrastructure” to build a Smart City; and the introduction of advanced environmentally-friendly reclamation technology. I believe that our departments will continue to proactively explore and adopt innovation and technology to enhance work performance and effectiveness, increase productivity, and improve quality.