My thanks to Maryam Ibrahim for supporting my views on Kalabagh dam and giving the comparative costs of thermal and hydel power. Another point that needs to be stressed is that burning of fossil fuels in thermal generation can cause very serious environmental consequences. Iftikhar Ali has raised the point about very poor quality of water carrying all kinds of dangerous chemicals. What needs to be remembered is that with the much reduced flow in the rivers, canal and waterways, the same amount of affluent as before is causing much more pollution. We badly need more dams to send more water down the canals and waterways to 'cleanse' them better. -KHURSHID ANWER, Lahore, via e-mail, September 25.