A similar entry appears in the Wheel of Time Companion confirming the information available in the main story arc.
The Alguenya is a large river, whose source is north of Cairhien. It passes through close to the city of Cairhien, where docks supply the city and eventually joins the Erinin at Aringill. Tributaries of the Alguenya include the River Gaelin. Kerene Nagashi was supposedly on the Alguenya when she was murdered by the Black Ajah (NS, Ch. 18). In earlier times, the border between Shandalle and Tova roughly followed the Alguenya.