The nothern plains is a densly populated division why

The northern plains of India are densely populated because of the following reasons:

They consist of large plain of alluvial soil and the deposition of alluvium in a vast basin lying at the foothills of the Himalaya over millions of years make this plain fertile.It spreads over an area of 7 lakh square kilometres, is 2,400 kilometres long, 240 to 320 kilometres broad and are flat lands which make staying simple for the people.They are made up of three major river systems, namely - the Indus, the Ganga and the Brahmaputra along with their tributaries. This helps in increasing the agricultural produce.