Navi Mumbai’s primary drinking water source, the Morbe Dam, has not undergone desilting, even though silt accumulation in reservoirs reduces their water storage capacity. This information was revealed through a Right To Information (RTI) Act inquiry.
The failure to desilt has resulted in misleading information about the dam's water capacity, potentially causing authorities to become complacent, said the NatConnect Foundation, an environmental watchdog that obtained this data.
This revelation coincides with the Brihanmumbai Municipal Corporation (BMC) admitting to NatConnect that it does not desilt its lakes and reservoirs. According to NatConnect director B.N. Kumar, this lack of maintenance may explain the water cuts that occur from April to May, even as dams and lakes overflow during the monsoon.
Kumar highlighted that the Central Government has informed the Lok Sabha that rivers naturally carry and deposit silt based on various factors such as discharge, slope, and morphology. The government stated in April last year that silt accumulation in reservoirs leads to reduced water storage capacity.
NatConnect has asked both the BMC and the Navi Mumbai Municipal Corporation (NMMC) for details on desilting efforts in their respective reservoirs. The BMC disclosed that no desilting has been done at Vihar, Tulsi, Modak Sagar, Tansa, and Middle Vaitarna lakes over the past decade. There was no information provided regarding the desilting of the Bhatsa and Upper Vaitarna lakes. Together, these seven lakes supply 3.4 billion liters of drinking water daily to Mumbai.
In Navi Mumbai, the NMMC-owned Morbe Dam, which stands 88 meters high, supplies 450 million liters of water daily. Maruti Ambedkar, Deputy Engineer at Morbe Dam, confirmed in response to NatConnect's inquiry that no desilting has occurred at the dam since it was taken over by NMMC.
Kumar argued that the accumulation of silt in these water bodies leads to inaccurate data and a false sense of security among authorities, which in turn forces residents to rely on water tankers. He added that this situation fosters a multi-crore water tanker mafia in the city and its suburbs.
Disturbed by the lack of desilting, Kumar filed an RTI with the State Urban Development Department (UDD) to understand BMC's desilting operations. Shockingly, the UDD responded that it has no records of such activities, raising concerns about the state government’s oversight of essential services like drinking water supply. Kumar questioned the state’s planning, especially given the rapid urban expansion.
Kumar noted that while municipal corporations spend crores on desilting stormwater drains, they neglect desilting drinking water sources, ignoring the silt brought in by mountain streams and rivers. The Central Pollution Control Board (CPCB) has observed that cities like Mumbai and Chennai have experienced unprecedented flooding due to inadequate flood protection, reduced water holding capacity of reservoirs due to siltation, riverbank breaches, and raised riverbeds.
Nandakumar Pawar, head of the environmental NGO Shri Ekvira Ari Pratishtan, agreed with the need for desilting, stating that the absence of desilting contributes to dam overflows and subsequent river flooding. He also noted that sludge from reservoirs, rich in minerals, could be used to enhance the topsoil of farmland.