The Aiwa or Eigə River is one of the largest rivers in Peilaš and the central artery of the Edastean sphere. Its source is high in the Eiwəl Gourun; it runs east and south through Lasomo eventually draining in a large delta in the center of Kasca. Major tributaries include the Thabīa, the Bwimbai, and the Milīr. In the earliest record the valley was inhabited by tribes of the Eigə Valley linguistic group, who eventually gave rise to Ngauro civilization, and whose classical-era descendants are represented by the Miw.
In the late 3rd millennium BP Talo-Edastean tribes poured out of the Bwimbai, and the Ndak became settled on the middle Aiwa. Their subsequent imperial expansion against surrounding tribes led to the replacement of Eigə Valley-speakers on the lower and middle Aiwa, though a group known as the Meshi remained, for a time, on the upper Aiwa.
|Adāta||Ēza||[ˈeːza]||← NT Aiwa|
|Fáralo||Eigə||['e.ɡə]||← NT Aiwa|
|Naidda||Ya||['ja]||← NT Aiwa|
|Wippwo||Ha||['ha]||← Ndd. Ya|
|Ndok Aisô||Oigeu||['ɔːj.ɣɛw]||← NT Aiwa|
|Buruya Nzaysa||Iwa||['i.wa]||← NT Aiwa|
|Æðadĕ||Ēz||[eːz]||← Ad. Ēza|
|Mešmo Koyʔōn||Īla||[ˈiː.lɐ]||← Ad. Ēza|
|Pencek||Eka||[əˈɡaː]||← F. Eigə (borrowed)|
|Namɨdu||Yogga||['jʌɡ.ɡɐ]||← F. Eigə|