Temporal changes in the flow route of the Great Menderes River and the uses of the oxbow

Objective: Wetlands, which are one of the most important surface water resources, are of great importance for many reasons such as their unique biological diversity, flood control, positive effects on climate characteristics and their contributions to the country's economy. In this study, it is aimed to determine the changes in the flow route of the Great Meandros River and the resulting wetland oxbow with remote sensing and geographic information systems. The current use of oxbow has been revealed by physical and chemical analysis. Material and Methods: In the study, standard topographic maps, Landsat-5, Landsat-8 and Sentinel-2 satellite images were used as basic cartographic material. Soil, sediment and water samples were taken at predetermined locations, and analysed. After geocorrection and mosaicing the bases were created on the topographical maps dated 1980, 1996 and 2012. Contours, streams, rivers and oxbows on the maps were digitized and transferred to the database. Water and sediment sampling was carried out from 18 different oxbows determined on the base maps, and soil sampling was carried out from 3 different depths from those filled for agricultural use. Supervised and unsupervised classification, NDWI and MNDWI analyzes were performed on satellite images dated 1985, 1990, 2010, 2015 and 2020. Results: The changes that occurred in the Meandros river and the horn lakes in 32 years were determined from the digitized data. It has been determined that the success of NDWI and MNDWI analyzes in the detection of water surfaces by remote sensing is higher than the classification methods. The soils in the closed horn lakes are generally loamy, slightly alkaline, unsalted and moderately to highly calcareous, and the sediment samples are in the silty loam, slightly alkaline, calcareous and slightly salty class. In terms of macro and micro element contents, no significant problem was encountered except boron. The water samples were mostly classified as high quality and less polluted. In terms of nitrate nitrogen, there is pollution in more than half of the samples. Conclusion: In the study area, the Meandros river's flow route changed spatially by 18,58% between 1980 and 2012 as a result of meandering and human interventions, and this decrease continued until 2020. Oxbows showed an increase of 10.93% in the first 16 years and a decrease of 19.82% in the following 16 years. It was determined that NDWI and MNDWI methods gave successful results at a rate of 84% in the determination of water surfaces in the river system, but they could not be successful in large areas in oxbows. It was concluded that oxbows should be protected for ecological balance and their misuse should be prevented.