Sapta-Sindhu meaning 7 rivers, is the term which gave birth to the word "Hindu". Sapta-Sindhu was referred to as Hapta-Hindu by Persians etc. The people of this region and culture, the Sapta-Saindhavas were referred to as Hapta-Haindavas by Persians etc. The term is found in Avesta of Zoroastrians.
Scholars are not of the same opinion on the names and identity of the seven rivers of Sapta Sindhu. Most of the scholars agree that the heartland of Rigvedic Aryans was modern Afghanistan, Punjab (Pakistan & India), Haryana & Rajasthan. Further, Kubha River (Kabul), Suwastu (Swat) Kramu (Kurram) & Gomati (Gomal) Rivers have also got a place in texts. The Ganga & Yamuna which were mentioned in later Vedic texts indicated the eastern boundary of the Sapta Saindhava Region.
There is a verse in Nadistuti Sukta of Rigveda, hymn of praise of rivers which mentions the following 10 rivers: Ganga, Yamuna, Sarasvati, Sutudri, Parusni, Asikni, Marudvrdha, Vitasta, Arjikiya, Susoma. The Shutudri was Sutlej, Parushni was Ravi, Asikni was Chenab and Vitasta was Jhelum.
The majority of the scholars believe that Sindhu & Saraswati (located in Rajasthan) were the most popular and sacred rivers of that era. Some scholars are of the opinion that the hymns in praise of the Saraswati are probably some of the oldest, composed more than 8000 years ago. The 5 rivers Sutudri, Parusni, Asikni, Vitasta, Vipas, all were tributaries of Sindhu River. Together with Saraswati and Sindhu, these 5 rivers constituted the Sapta Sindhu.
However, Saraswati has been mentioned as Saptasvasa, which means she with 7 sisters. So, This further leads to a group of 8 Rivers.