Analyzing water level changes in Prespa Lake with geospatial tools

The Ohrid-Prespa lake system, dating back over 4 million years, is the oldest permanent lake system in Europe. This study focuses on Lake Prespa, a transboundary tectonic lake shared by North Macedonia, Albania, and Greece, which has experienced significant water loss in recent decades due to its sensitivity to external factors such as climate change. Historically, Lake Prespa had a mean depth of 14 m and a maximum depth of 48 m prior to the observed decline in water levels. This research examines changes in the surface extent of Lake Prespa and surrounding vegetation from 1984 to 2023 using satellite imagery, including Landsat 5 and 8 (USGS) and Sentinel-2 (Copernicus Programme). Advanced geospatial analyses were conducted to assess water occurrence, change intensity, seasonality, and maximum water extent. These data provide insights into the spatial and temporal dynamics of surface water, capturing inter-annual variability and long-term trends. An integral component of this research involved a practical project conducted with 10th-grade students. Through collaborative efforts, we explored water-level changes in Lake Prespa over multiple periods, applying GIS and satellite technologies to create thematic models of seasonal water variations over time. This initiative not only enriched the educational experience of the students but also demonstrated the capacity to monitor Lake Prespa effectively and analyze the potential causes of its water-level decline. Hence, the analysis shows that Lake Prespa lost 18.87 km² of surface area, or 6.9% of its total surface, decreasing from 273.38 km² (June 1984) to 254.51 km² (July 2023). The most recent imagery from August 2024 shows a surface area of 252.9 km². The rate of water loss was higher in the periods 1987–1993 and 1998–2004, while the lake's surface area has not varied in the last decade. It is crucial for us, as geoscience educators, to integrate advanced geospatial technologies such as GIS, geoinformatics, and remote sensing into our teaching in the geosciences field. By employing these tools, we can provide our students with hands-on experience in applying cutting-edge methods while deepening their understanding of geosciences through analytical and practical approaches. This project proved highly motivational for my students, as it enabled us to utilize new technologies to explore geoscience topics, learn innovative methods, and uncover original data previously unreported. The process not only inspired the students to engage in scientific discovery but also underscored the value of using modern tools to produce new and meaningful research outcomes. Key findings include a simple mapping of persistent water surfaces, areas with intermittent water presence, and the intensity of changes between two distinct time periods (1984–1999 and 2000–2023). Results reveal notable patterns of water reduction, seasonal shifts, and localized variability.