Rivers drying up

About thirty or forty years ago most of the rivers of Bangladesh or Bengal basin were in full stream and they never dried up even in the dry season. But what is happening now? Except the rainy season, most of the rivers become dry or almost dry; some are spotted with many 'chars'. Once upon a time the rivers which now are almost dry were flowing with big vessels, cargoes and even ships. Will those days come again? We should reveal the causes behind this. When discussion takes place about this issue, most of our politicians blame the Farakka Barrage and lack of dredging activities. But the causes need further elaboration. Yes, Farakka is one of the main causes but it is not the whole truth. And another thing is lack of dredging. But dredging technology came to us not long ago. Then how hundreds and thousand of rivers of our country flowed smoothly without dredging in the past? So it is totally foolish to identify lack of dredging as the main reason behind the rivers getting dried up.
There are many other reasons and most of them have been created by us. not by others. For example, construction of sluice-gates is obstructing the normal flow of rivers.