Inland Waters Unveiled: Exploring Water Surface Elevation in Peninsular Malaysia Using Satellite Sentinel-3 SRAL Altimeter

Continuous monitoring of inland water resources is vital for sustainable management, especially during water scarcity events like El Niño in Malaysia. However, a research gap exists in studying small to medium-scale reservoirs using small footprint altimeters. This study proposes using the Satellite Sentinel-3 SRAL Altimeter (S3 SRAL) to retrieve accurate water surface elevation (WSE) time series. The methodology involves data processing with the SARvatore toolkit, WSE retrieval using proposed equations, data masking using lake boundaries, construction of WSE time series, and validation through comparison with S3 SRAL data and in situ gauge measurements. The primary objectives are to retrieve inland water surface elevation and validate data accuracy using regression, correlation coefficient (R2), and root mean square error (RMSE) evaluation. Promising outcomes were obtained from research on small reservoirs in Peninsular Malaysia (< 150 km2). S3 SRAL measurements showed strong agreement with gauged levels, indicating high correlation and low error rates. Temengor Reservoir (137.25 km2) exhibited robust results (R2 = 0.99, RMSE = 59.95 cm), while Chenderoh Reservoir (8.55 km2) had slightly lower values (R2 = 0.74, RMSE = 79.64 cm). The same methods were applied to the largest reservoir in Peninsular Malaysia, Kenyir Reservoir (326.38 km2), highlighting the effectiveness of S3 SRAL. Historical S3 SRAL data since 2016 aided reservoir and lake management decisions and supported research on water level and climate change.