How many the aflaj irrigation systems are used today in Oman?

The Aflaj Irrigation Systems of Oman are ancient water channels from 500 AD located in the regions of Dakhiliyah, Sharqiyah and Batinah. According to UNESCO, more than 3 thousand aflaj are still in use in Oman today. Nizwa, the former capital city of Oman, was built around a falaj which is in use to this day. These systems date to before the Iron Age in Oman.