A Savior in the Monsoon Season

30 submersible motor pumps against the floods

India's monsoon is both a curse and a blessing. While agriculture relies on natural water supply, the residents and infrastructure of Mumbai suffer from the enormous water deluge. Nearly thirty axial submersible motor pumps from Wilo are operating in four different water pumping stations, facing the challenge during the rainy season.

Mumbai is vast. It is diverse. The city, formerly known as Bombay, is not only India's economic hub; it also combines a productive film industry, diverse areas, and a tropical forest within an urban zone. Situated on a peninsula on Bombay Island, Mumbai is one of the largest and most densely populated megacities in the world. The city's climate is typically warm and humid, but from June to September, strong winds from the southwest bring the monsoon season. This phenomenon is perceived in different ways - while it revitalizes the arid environment and restores the beauty of nature, regions are plagued by floods and heavy monsoon rains that cause devastating landslides and damage public infrastructure. Currently, Mumbai is the only city in India with rainwater pumping stations. During high water levels, these stations discharge water from a drainage system or a water body into the sea, while flood gates prevent seawater from entering the city. Through the "Brihanmumbai Stormwater Disposal" (Brimstowad) project, Wilo India has currently equipped four out of eight stations. "Wherever the land level is below sea level, waterlogging is inevitable. Pump stations are primarily responsible for two things: pumping out rainwater and preventing the flood from entering the city. Each pump can discharge 6,000 liters of water per second," says Rajesh Unde from Wilo India. "We are more than pleased to have designed, manufactured, tested, assembled, and commissioned our axial flow submersible pumps for these stations."

Axial submersible motor pumps as a solution

Tidal gates should be designed to function automatically, i.e., they open or close depending on the tide and flow conditions. During low tide, the gates need to remain open to allow the floodwater to flow through the drainage into the sea. However, as the tide rises, the gates are closed, and the water enters the planned rainwater pumping station through the inlet bay and screens. The floodwater is then pumped into the outlet channel of the pumping station towards the sea. In case of flooding, the flow is restricted, and tidal gates need to be installed to prevent water from entering the drainage and pumping station. Wilo India has been involved in the project from the planning phase to support and ensure the smooth operation and performance of all pumps provided on-site. "Our axial submersible motor pump was the optimal solution for the requirements within the project. Its own weight ensures a self-centering fit in the discharge pipe, and despite its size, it is easy to install," explains Rajesh Unde. "Temperature monitoring, vibration sensors, thermal motor protection, and leak sensors in the motor ensure high reliability even under challenging operating conditions." In addition to providing the complete pump technology for the pumping stations, Wilo also performs comprehensive service. Service technician visits are scheduled quarterly, and Wilo conducts inspections before and after the monsoon season to ensure the smooth operation of all pumping systems. The Wilo service experts are on standby in case of emergencies and regularly monitor the pumps.

Tidal range fluctuations pose significant challenges

Low-lying areas in Mumbai, such as Milan Subway Road and Hindmata Junction, are particularly vulnerable to flooding as the stormwater drains cannot discharge water into the sea or a river. The coastal city also has to deal with fluctuations in tidal range, which poses a significant challenge for discharging rainwater into the sea. Mumbai's drainage system is over 100 years old, at least in some parts of the city. The entire system consists of 2,000 km of open drains, 440 km of closed drains, 186 outlets, and more than 30,000 water inlets. Mumbai's rainwater drainage network is extensive, covering a total area of approximately 438 km². During the monsoon season, the coastal city receives over 3500 mm of precipitation. The intensity, frequency, and duration of rainfall have worsened over the years. The capacity of most drains is around 25 mm of rain per hour during low tide, which is routinely exceeded in Mumbai during the monsoon season.