PlanetScope Imagery-based Monitoring of Annual and Seasonal Dynamics of Lakes in Tbilisi, Georgia

Lakes have special aesthetic and recreational value in Tbilisi, especially in recent years, as the demand for residential areas near water bodies and the load on the surrounding landscapes have increased. Monitoring smallarea water bodies requires high spatial and temporal resolution images. For more precise research, the PlanetScope imagery (3 m) provides excellent data. We recorded the annual and seasonal dynamics of the lake area extent of four lakes in Tbilisi using PlanetScope optical satellite images. The changes observed in the NDVI and NDWI based on the four-season images in ArcMap 10.8.2 for the period of 2017–2023 revealed an interesting trend. Despite the increasing severity of droughts in Tbilisi over the last 30 years, Turtle Lake, which is located hypsometrically high and surrounded by forest landscapes, is the most resistant to annual and seasonal changes. Didi and Patara Lakes, located in steppe landscapes, were particularly vulnerable to changes. Lisi Lake exhibited a similar trend. Changes in lakes located in steppe landscapes have a special seasonal character, and therefore, a noticeable decrease in water level coincides with the summer dry season (August-September). In addition to natural conditions, land use changes are also important. Active development is underway near these lakes. The alarming dynamics of the lake area extent of these lakes confirm that research is important in future conservation decisions for these lakes and their ecosystems.