India, Sept. 28 -- A sharp increase in mud and sediment in the Ulhasnagar river over the past 10 days has repeatedly clogged pumps at filtration plants, reducing treated-water supply by around 20% to Badlapur, Ambernath, Ulhasnagar and Kalyan. Officials suspect illegal sand-mining activity along the river may have contributed to the increase in sediment, though this has not been established.

The river supplies drinking water to the four areas and has become increasingly murky since the beginning of the Ganesh festival, according to officials.

The Badlapur water department has warned that some areas may face reduced water supply for a few more days as the treatment plant operates at lower capacity.

Suresh Kadri, an official with the Mah...