The Drainage Services Department (DSD) said on Tuesday that it has purchased three extra pumping robots, costing about HK$3 million in total, to help cope with the increasing frequency of extreme weather events in Hong Kong.

Torrential rains have struck the city in recent weeks, prompting the observatory to issue four black rainstorm warnings within just eight days.

The department already has three “mobile powerful pumping robots,” all of which were deployed last week to address severe flooding incidents at locations including Queen Mary Hospital, an underground tunnel near Tai Po Station and a car park in Tseung Kwan O.

Officials said once the robots were deployed, most floods were resolved within one to two hours.

Each robot can pump 800 cubic metres of water per hour, equivalent to one-third of the volume of a standard-sized swimming pool.

They can operate continuously for eight hours and are designed to cope with complex terrain such as stairs and slopes.

When asked how the department decides which locations get priority for the robots, senior engineer Leo Chan said it is hard to pick individual places due to the unpredictability of flooding locations.

“There is great uncertainty in rainstorm events and we are not able to predict where the flooding incident is going to be,” he said.

“So we are going to place the robots strategically in our bases. Our goal is to get to the flooding locations as soon as possible once we receive the service call.”

The robots do have limitations, such as only being able to handle floodwaters up to 60 centimetres deep, Chan said.

To deal with rapidly rising water levels, the department deploys another model of pumping robot, which is smaller but can operate on both land and water, he added.

Chan said more than 30 of the department's staff have been trained to operate water pumping robots and there are plans to arrange training for more employees.