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

Study region Lakes in Mainland Southeast Asia (SEA) Study Focus 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). New Hydrological Insights for the Region 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.