DISCOVERY NARRATIVE: LAKE MANGGUANG From Toponymic Anomalies to Paleo Lake Reconstruction: Forensic Epistemology of Hidden Landscapes in Pasaman and the Discovery of the Original Name Lake Mangguang

This narrative documents the methodological journey from observing toponymic anomalies in a dry,hilly landscape to reconstructing a paleo lake system through precise elevation-based hydrological modeling. The key discovery is the identification of the toponym Muaro Mangguang not as an arbitrary name, but as the natural outlet of the lake itself. By extracting the core word Mangguang,the original name of the lake is obtained: Lake Mangguang (Danau Mangguang). The reconstruction shows that Lake Mangguang encompassed the Graben Rao Basin and the Graben Lubuk SikapingBasin, with a catastrophic breach at Bukit Putus that drained the lake eastward toward the Rokan River. This reconstruction is validated by Dutch colonial documentation, particularly the testimony recorded by Paul Adrian Daum in Tijdschrift voor het binnenlandsch bestuur (1904)