|River Ganges in Rishikesh|
So they cut very deep gorges where they cross the Himalayan ranges and thus they have developed antecedent drainage. An antecedent stream maintains its original course and pattern despite the changes in underlying rock topography. These rivers are fed not only by monsoon rains during the month of June to September, but also by the glaciers round the year.
The Ganga (about 2071kmlong) and is eight major tributaries -- the Yamuna, Ramaganga, Sarda, Gharghara, Rupti, Gandak, Bagmoti and Kosi, Mahananda, Chambal emerging out of the Himalaya flow eastwards over the Ganga plains. The Yamuna and Son are its major right bank tributaries.