Sir — The capital city is often faced with complete stoppage of water supply due to the closure of water treatment plant,s as ammonia content in water in Yamuna has been abnormally high. Such interrupted water supply was hardly seen in yesteryears. Reports indicate that the high ammonia content in river water is due to the industrial waste that comes from factories in Panipat. The Centre should direct the Haryana Government to take immediate steps to control industrial waste that passes into the Yamuna and comes to Delhi.