In Hattusa's texts, CTH68, which describes the limits of the country of Mira, the rivers Astarpa and Siyanta form the boundaries of the country of Mira: "the land of Kuwaliya will be your frontier. [...] You will not installed any city on the Astarpa river or on the Siyanta river ...". So, the Siyanta river country is confused with the Kuwaliya, the classic Kabalis.
Siyanta probably comes from a city name, which I think corresponds to the classic Sinda. The city was situated on an island upstream of this river, which in classical literature is called Caularis, a tributary of the present Dalaman.
Under the Greco-Roman period, Sinda was known to be in the extreme west of Pisidia, in the vicinity of Cibyra, which was in Phrygia or in an independent region called Kabalis.The ruins of Sinda, also called Isinda, are located on the present commune of Korkuteli.
During the expedition of the consul Manlius, reported by Titus Livius and Polybius, the Roman army, starting from Cibyra, first crossed the territory of Sinda to go to Galatia.
My notes of veracity :
The river Siyanta was the current Dalaman: 3/5
Siyanta was the classic Sinda in Kabalis: 2,5 / 5