Long-term spatial and temporal patterns of lake surface water extent in mainland Southeast Asia

Lakes in Mainland Southeast Asia (SEA) Lakes are sensitive indicators of climatic conditions, reflecting environmental shifts and offering insights into climate change impacts. This study investigated changes in lake surface water extent (LWE) across 651 lakes in mainland SEA, a region highly vulnerable to climate change. A 36-year monthly time series (1984–2019) of LWE derived from Global Surface Water products was used to map and analyze these changes. A semi-automated approach delineated and mapped LWE changes, producing three datasets: a discontinuous monthly LWE dataset (SEA-LWEun), a gap-filled continuous monthly LWE dataset (SEA-LWEgf), and a gap-filled, smoothed version (SEA-LWEsm). The continuous datasets enabled detailed monthly and annual LWE analysis, including seasonal variation. Accuracy was assessed using RMSE, MAE, Bias, and NSE, with comparisons to global datasets. By addressing earlier discontinuities, this study improves regional LWE change assessments, revealing a net positive LWE change across SEA. Specifically, 192 lakes showed a significant average increase of 0.004 km²/year (total gain: 24.9 km²), while 127 lakes saw an average decrease of −0.002 km²/year (total loss: 10.8 km²). The SEA-LWE dataset, provided in GIS-ready vector format, fills key gaps in long-term hydrological data, advancing our understanding of climate variability’s impacts on LWE over the past three decades. • Developed the monthly SEA-LWE dataset for 650 + lakes across Southeast Asia. • The SEA-LWE provides 36-year (1984–2019) LWE records from Landsat-derived GSW data. • Addressed cloud-cover biases in tropical lake surface-water area analysis. • 192 lakes increased by 0.004 km²/yr; 127 lakes decreased by 0.002 km²/yr. • Northern basins (Mekong and Chao Phraya) showed strongest LWE variations.