Why it belongs here
The Casei River (Spanish: Río Casei), sometimes also spelled Casey River (Río Casey), is a tributary of the Añasco River (Río Grande de Añasco) that flows through the municipalities of Las Marías, Mayagüez and Añasco in western Puerto Rico. It originates in the mountains of Las Marías, from where it flows northwest towards the Añasco Valley, creating a natural municipal boundary between Las Marías and Mayagüez along its path.
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