The upper catchment area (UCA) plays a crucial role in hydrology, geomorphology, and glacial lake hazard assessment research. While manual digitization remains the most common method for extracting the UCA in small study areas, it is often labor-intensive and time-consuming. Automated estimation techniques have been utilized at regional scales, but their accuracy remains limited in alpine terrains, particularly around glacial lakes. To address this limitation, we developed an improved approach, implemented in ArcGIS Model Builder, to extract the outlet and UCA of glacial lakes automatically using a digital elevation model (DEM) and a glacial lake dataset from circa 2020. To evaluate the method, we mapped 963 glacial lakes with a total area of 59.75 +/- 6.95 km2 in four test watersheds using 18 images from Landsat 8. A total of 264 glacial lakes, varying in size from 0.02 to 5.83 km2, were identified as potentially dangerous for testing based on three filtering criteria. The calculated outlets and UCAs, validated by visually digitized references, indicate that our approach achieves an accuracy of 93.68 +/- 2.12 %, significantly improving over previous methods. Our approach is more efficient and accurate than previous methods, offering researchers a reliable tool. Our developed techniques and tools can be broadly applied to glacial lake hazard assessments and related hydrological research.