Spatio-temporal changes of lake water extents in Lakes region (Turkey) using remote sensing

Thesis Type: Postgraduate

Institution Of The Thesis: Middle East Technical University, Graduate School of Natural and Applied Sciences, Turkey

Approval Date: 2019

Thesis Language: English


Principal Supervisor (For Co-Supervisor Theses): Koray Kamil Yılmaz

Co-Supervisor: Mehmet Lütfi Süzen


Monitoring inland water bodies has been one of the most popular practices in remote sensing. Changes in water extents of lakes are especially important due to strong links to sustainable water resources management and ecosystem services. Considering that the Mediterranean region is a hot spot of climate change (IPCC, 2013), monitoring of lakes become more crucial. This study investigates the spatio-temporal changes in water extents of 16 lakes in the Lakes Region, Turkey using remote sensing techniques for the 1984-2018 time period. The analysis was performed within Google Earth Engine® - a cloud-based geospatial data processing platform. The remotely sensed imagery utilized consisted of all the cloud free (less than 10%) images from Landsat and Sentinel-2 platforms available for the study area and period. Normalized Difference Water Index (NDWI) was used to delineate water extent from the image inventory. Bathymetry data was used with lake level measurements to calculate variation in area and volume of lakes. Areas calculated with remote sensing images were than compared with areas calculated via in-situ measurements. Results showed that lake extents obtained from in-situ lake level measurements were generally higher than those estimated from remotely sensed images, with correlation coefficient values ranging between 0.04 and 0.93. Furthermore, the relationship between spatio-temporal variations in the lake extents and hydrometeorological variables, such as precipitation and evaporation, were investigated. According to these analysis in Lake Eber, Lake Ilgin, Lake Beysehir, Lake Acigol, Lake Karatas, Lake Akgol, Lake Karamik and Lake Gavur; water extents have a positive correlation with precipitation and negative correlation with evaporation. Analysis indicated that In Lake Burdur and Lake Aksehir water extents decreased continuously since 1984. Seasonal fluctuations in water extents were identified for Lake Salda, Lake Beysehir, Lake Yarisli, Lake Kovada, Lake Acigol, Lake Ilgın, Lake Karatas, Lake Karamik, Lake Eber and Lake Akgol. In Lake Egirdir, Lake Salda, Lake Beysehir and Lake Sugla water extent did not fall below %90 of their maximum extent at the end of the study period (2017).