Indravati is a tributary of the Godavari River, flowing through Chhattisgarh and Maharashtra, and is NOT part of the Ganga river system. Son, Gomati, and Yamuna are all major tributaries of the Ganga - Son joins Ganga near Patna, Gomati is a Himalayan tributary in UP, and Yamuna is the largest tributary meeting Ganga at Allahabad (Prayagraj).